Imperial College London

Nicholas M Harrison

Faculty of Natural SciencesDepartment of Chemistry

Chair of Computational Materials Science
 
 
 
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Contact

 

+44 (0)20 7594 5884nicholas.harrison Website

 
 
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Location

 

401LMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

316 results found

Bower R, Wells MP, Johnson F, Kilmurray R, Doiron B, Calì E, Mallia G, Zou B, Mihai AP, Harrison NM, Fearn S, Oulton R, Alford NM, Cohen LF, Petrov PKet al., 2021, Tunable double epsilon-near-zero behavior in niobium oxynitride thin films, Applied Surface Science, Vol: 569, Pages: 150912-150912, ISSN: 0169-4332

Journal article

Alaithan ZA, Harrison N, Sastre G, 2021, Diffusivity of Propylene in One-Dimensional Medium-Pore Zeolites, The Journal of Physical Chemistry C, Vol: 125, Pages: 19200-19208, ISSN: 1932-7447

Journal article

Kousar K, Walczak MS, Ljungdahl T, Wetzel A, Oskarsson H, Restuccia P, Ahmad EA, Harrison NM, Lindsay Ret al., 2021, Corrosion inhibition of carbon steel in hydrochloric acid: Elucidating the performance of an imidazoline-based surfactant, Corrosion Engineering Science and Technology, Vol: 180, Pages: 1-8, ISSN: 0007-0599

A combination of electrochemical measurement and interface analysis have been applied to characterise the interaction of OMID, an exemplar imidazoline-based corrosion inhibitor, with carbon steel in 1 M hydrochloric acid. Corrosion inhibition efficiency data indicate that excellent performance is achieved well below the critical micelle concentration. High resolution X-ray photoelectron spectra demonstrate that, as the corrosion rate decreases, the interface evolves towards one comprising OMID bound to film-free carbon steel. This latter result provides key input for those researchers attempting to predict corrosion inhibitor functionality through atomic scale interfacial modelling, and so identify next generation chemistries.

Journal article

Acres MJ, Hussain H, Walczak MS, Nikiel M, Sewell C, Rafols i Belles C, Ahmad EA, Walton AS, Muryn CA, Harrison NM, Lindsay Ret al., 2020, Core level photoemission line shape selection: Atomic adsorbates on iron, Surface and Interface Analysis, Vol: 52, Pages: 507-512, ISSN: 0142-2421

Robust fitting of core level photoemission spectra is often central to reliable interpretation of X‐ray photoelectron spectroscopy (XPS) data. One key element is employment of the correct line shape function for each spectral component. In this study, we consider this topic, focusing on XPS data from atomic adsorbates, namely, O and S, on Fe(110). The potential of employing density functional theory (DFT) for generating adsorbate projected electronic density of states (PDOS) to support line shape selection is explored. O 1s core level XPS spectra, acquired from various ordered overlayers of chemisorbed O, all display an equivalent asymmetric line shape. Previous work suggests that this asymmetry is a result of finite O PDOS in the vicinity of the Fermi level, allowing O 1s photoexcitation to induce a weighted continuum of final states through electron‐hole pair excitation. This origin is corroborated by O DFT‐PDOS generated for an optimised five‐layer Fe(110)(2 × 2)‐O slab. Adsorbate DFT‐PDOS were also computed for Fe(110) urn:x-wiley:01422421:media:sia6770:sia6770-math-0001 ‐S. As, similar to adsorbed O, there is a significant continuous distribution of states about the Fermi level, it is proposed that the S 2p XPS core levels should also have asymmetric profiles. S 2p XPS data acquired from Fe(110) urn:x-wiley:01422421:media:sia6770:sia6770-math-0002 ‐S, and their subsequent fitting, verify this prediction, suggesting that DFT‐PDOS could aid line shape selection.

Journal article

O'Hara EM, Phelan B, Osgerby S, Barrett RA, Raghavendra R, Leen SB, Harrison NMet al., 2020, Experimental and computational characterization of the effect of manufacturing-induced defects on high temperature, low-cycle fatigue for MarBN, MATERIALIA, Vol: 12, ISSN: 2589-1529

Journal article

Dovesi R, Pascale F, Civalleri B, Doll K, Harrison NM, Bush I, D'Arco P, Noel Y, Rerat M, Carbonniere P, Causa M, Salustro S, Lacivita V, Kirtman B, Ferrari AM, Gentile FS, Baima J, Ferrero M, Demichelis R, De La Pierre Met al., 2020, The CRYSTAL code, 1976-2020 and beyond, a long story, Journal of Chemical Physics, Vol: 152, Pages: 1-34, ISSN: 0021-9606

CRYSTAL is a periodic ab initio code that uses a Gaussian-type basis set to express crystalline orbitals (i.e., Bloch functions). The use of atom-centered basis functions allows treating 3D (crystals), 2D (slabs), 1D (polymers), and 0D (molecules) systems on the same grounds. In turn, all-electron calculations are inherently permitted along with pseudopotential strategies. A variety of density functionals are implemented, including global and range-separated hybrids of various natures and, as an extreme case, Hartree–Fock (HF). The cost for HF or hybrids is only about 3–5 times higher than when using the local density approximation or the generalized gradient approximation. Symmetry is fully exploited at all steps of the calculation. Many tools are available to modify the structure as given in input and simplify the construction of complicated objects, such as slabs, nanotubes, molecules, and clusters. Many tensorial properties can be evaluated by using a single input keyword: elastic, piezoelectric, photoelastic, dielectric, first and second hyperpolarizabilities, etc. The calculation of infrared and Raman spectra is available, and the intensities are computed analytically. Automated tools are available for the generation of the relevant configurations of solid solutions and/or disordered systems. Three versions of the code exist: serial, parallel, and massive-parallel. In the second one, the most relevant matrices are duplicated on each core, whereas in the third one, the Fock matrix is distributed for diagonalization. All the relevant vectors are dynamically allocated and deallocated after use, making the code very agile. CRYSTAL can be used efficiently on high performance computing machines up to thousands of cores.

Journal article

Otter J, Brophy K, Palmer J, Harrison N, Riley J, Williams D, Larrouy-Maumus Get al., 2020, Smart surfaces to tackle infection and antimicrobial resistance, Briefing Paper

Report

Abualnaja F, Hildebrand M, Harrison NM, 2020, Ripples in isotropically compressed graphene, Computational Materials Science, Vol: 173, Pages: 1-5, ISSN: 0927-0256

An isotropic compression of graphene is shown to induce a structural deformation on the basis of Density Functional Perturbation Theory. Static instabilities, indicated by imaginary frequency phonon modes, are induced in the high symmetry -K (zigzag) and -M (armchair) directions by an isotropic compressive strain of the graphene sheet. The wavelength of the unstable modes (ripples) is directly related to the magnitude of the strain and remarkably insensitive to the direction of propagation in the 2D lattice. These calculations further suggest that the formation energy of the ripple is isotropic for lower strains and becomes anisotropic for larger strains. This is a result of graphene’s elastic property, which is dependent on direction and strain. Within the quasi-harmonic approximation this is combined with the observation that molecular adsorption energies depend strongly on curvature to suggest a strategy for generating ordered overlayers in order to tune the functional properties of graphene.

Journal article

Chang V, Camino B, Noakes TCQ, Lorusso A, Perrone A, Harrison NMet al., 2020, Theoretical study of the influence of hydrides on the performance of Mg and Y photocathodes, Journal of Applied Physics, Vol: 127, Pages: 1-9, ISSN: 0021-8979

Our understanding of material properties in the broadest sense is based on our ability to observe and disentangle underlying mechanisms. This has been aided enormously by the discovery and exploitation of synchrotron radiation. The next generation of light sources will be based on free electron lasers with potentially much greater light intensity and time resolution. This requires the development of new photocathode materials with high quantum efficiency (QE) and low emittance that are chemically and mechanically robust. One prospect is the use of yttrium (Y) and/or magnesium (Mg) thin films, but here, a fundamental understanding of the photoemission process from realistic materials is lacking. Observations of photoemissive performance would appear to contradict simple models. It is well known that materials with a lower work function are expected to facilitate photoemission, but the measured QE of Mg is higher than that of Y despite its nominal work function (3.7 eV) being significantly higher than that of Y (3.1 eV). In this work, these apparently anomalous observations are explained and rationalized by combining a simple three-step model of photoemission with large scale density functional theory calculations to predict the QE for realistic models of both materials in a special chemical environment. This approach allows us to identify the material parameters that govern the efficiency of the photoemission process. A detailed comparison with the experimental data suggests that, in this case, hydride formation on the Y surface, invisible to most experimental probes, nevertheless has a surprisingly large influence and reduces the photoemission significantly.

Journal article

Tseng HH, Serri M, Harrison N, Heutz Set al., 2020, Properties and degradation of manganese(III) porphyrin thin films formed by high vacuum sublimation, Porphyrin Science By Women (In 3 Volumes), Pages: 924-931, ISBN: 9789811223556

Manganese porphyrins are of interest due to the optical, electronic and magnetic properties of the central metal ion, coupled to the low bandgap of the polyaromatic ring. These attractive characteristics are harnessed in solutions or in ultra-thin films, such as, for example, self-assembled monolayers. However, for devices, thicker films deposited using a controlled and reproducible method are required. Here we present the morphological, structural, chemical and optical properties of manganese(III) tetraphenylporphyrin chloride (MnTPPCl) thin films deposited using organic molecular beam deposition, typically employed to process analogue molecules for applications such as organic photovoltaics. We find, using a combination of UV-vis and X-ray photoelectron spectroscopies, that the sublimation process leads to the scission of the Mn-Cl bond. The resultant film is a Mn(II)TPP:Mn(III)TPPCl blend where approximately half the molecules have been reduced. Following growth, exposure to air oxidizes the Mn(II)TPP molecule. Through quantitative analysis of the time-dependent optical properties, the oxygen diffusion coefficient (D) ~1.9 × 10-17 cm2/s is obtained, corresponding to a slow bulk oxidation following fast oxidation of a 8-nm-thick surface layer. The bulk diffusion D is lower than for analogous polycrystalline films, suggestion that grain boundaries, rather than molecular packing, are the rate-limiting steps in oxidation of molecular films. Our results highlight that the stability of the axial ligands should be considered when depositing metal porphyrins from the vapor phase, and offer a solvent-free route to obtain reproducible and smooth thin films of complex materials for engineering film functionalities.

Book chapter

Tseng H-H, Serri M, Harrison N, Heutz Set al., 2019, Properties and degradation of manganese(III) porphyrin thin films formed by high vacuum sublimation, Journal of Porphyrins and Phthalocyanines, Vol: 23, Pages: 1515-1522, ISSN: 1088-4246

Manganese porphyrins are of interest due to the optical, electronic and magnetic properties of the central metal ion, coupled to the low bandgap of the polyaromatic ring. These attractive characteristics are harnessed in solutions or in ultra-thin films, such as, for example, self-assembled monolayers. However, for devices, thicker films deposited using a controlled and reproducible method are required. Here we present the morphological, structural, chemical and optical properties of manganese(III) tetraphenylporphyrin chloride (MnTPPCl) thin films deposited using organic molecular beam deposition, typically employed to process analogue molecules for applications such as organic photovoltaics. We find, using a combination of UV-vis and X-ray photoelectron spectroscopies, that the sublimation process leads to the scission of the Mn–Cl bond. The resultant film is a Mn(II)TPP:Mn(III)TPPCl blend where approximately half the molecules have been reduced. Following growth, exposure to air oxidizes the Mn(II)TPP molecule. Through quantitative analysis of the time-dependent optical properties, the oxygen diffusion coefficient (D) ∼1.9×10−17cm2/s is obtained, corresponding to a slow bulk oxidation following fast oxidation of a 8-nm-thick surface layer. The bulk diffusion D is lower than for analogous polycrystalline films, suggestion that grain boundaries, rather than molecular packing, are the rate-limiting steps in oxidation of molecular films. Our results highlight that the stability of the axial ligands should be considered when depositing metal porphyrins from the vapor phase, and offer a solvent-free route to obtain reproducible and smooth thin films of complex materials for engineering film functionalities.

Journal article

Ahmad EA, Chang H-Y, Al-Kindi M, Joshi GR, Cooper K, Lindsay R, Harrison NMet al., 2019, Corrosion protection through naturally occurring films: new insights from iron carbonate, ACS Applied Materials and Interfaces, Vol: 11, Pages: 33435-33441, ISSN: 1944-8244

Despite intensive study over many years, the chemistry and physics of the atomic level mechanisms that govern corrosion are not fully understood. In particular, the occurrence and severity of highly localized metal degradation cannot currently be predicted and often cannot be rationalized in failure analysis. We report a first-principles model of the nature of protective iron carbonate films coupled with a detailed chemical and physical characterization of such a film in a carefully controlled environment. The fundamental building blocks of the protective film, siderite (FeCO3) crystallites, are found to be very sensitive to the growth environment. In iron-rich conditions, cylindrical crystallites form that are highly likely to be more susceptible to chemical attack and dissolution than the rhombohedral crystallites formed in iron-poor conditions. This suggests that local degradation of metal surfaces is influenced by structures that form during early growth and provides new avenues for the prevention, detection, and mitigation of carbon steel corrosion.

Journal article

Napier IA, Chang V, Noakes TCQ, Harrison NMet al., 2019, From electronic structure to design principles for photocathodes: Cu-Ba alloys, Physical Review Applied, Vol: 11, Pages: 064061-1-064061-13, ISSN: 2331-7019

Producing a metal photocathode with a low work function (WF), low emissivity, and high quantum efficiency is a matter of importance in the design of the next generation of free-electron laser facilities. General rules for the design of appropriate materials are currently unclear and difficult to elucidate from observations of structure-composition relationships of known photocathodes. In this work, high-quality density-functional-theory electronic structure calculations and a simple physical model are employed to develop design rules for photocathodes based on metallic alloys. A theoretical study of metal alloys for photocathode applications is presented, in which high WF, stable copper is paired with low WF, unstable barium in two alloys, Cu13Ba and CuBa. Surfaces terminating in a plane of Ba atoms have a lower computed surface energy than those terminating in Cu atoms due to surface segregation of the larger Ba atoms. This results in a significant surface dipole due to the interatomic charge transfer from the differences in electronegativity of the species. The details of the surface structure determine the direction of the dipole and thus have a strong influence on the computed WF. The computed WF of the Cu13Ba Ba-terminated (100) surface is even lower than that of pure Ba, at 1.95 eV. The computed quantum efficiency (QE) of the best-performing pure Cu surface is 5.86×10−6, whereas the best-performing Cu13Ba surface terminates in a plane of Ba atoms and has a significantly increased QE of 5.09×10−3. A surface terminating in two planes of Ba atoms, the (001) surface of CuBa, has an even higher computed QE of 1.38×10−2.

Journal article

Ignatans R, Mallia G, Ahmad EA, Spillane L, Stoerzinger KA, Shao-Horn Y, Harrison NM, Tileli Vet al., 2019, The effect of surface reconstruction on the oxygen reduction reaction properties of LaMnO3, The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, Vol: 123, Pages: 11621-11627, ISSN: 1932-7447

Perovskites have been widely studied for electrocatalysis due to the exceptional activity they exhibit for surface-mediated redox reactions. To date, descriptors based on density functional theory calculations or experimental measurements have assumed a bulk-like configuration for the surfaces of these oxides. Herein, we probed an initial exposed surface and the screened subsurface of LaMnO3 particles, demonstrating that their augmented activity toward the oxygen reduction reaction (ORR) can be related to a spontaneous surface reconstruction. Our approach involves high energy resolution electron energy loss spectroscopy for the fine structure probing of oxygen and manganese ionization edges under electron beam conditions that leave the structure unaffected. Atomic multiplet and density functional theory calculations were used to compute the theoretical energy loss spectra for comparison to the experimental data, allowing to quantitatively demonstrate that the particle surface layers are La-deficient. This deficiency is linked to equivalent tetrahedral Mn2+ sites at the reconstructed surface, leading to the coexistence of +3 and +2 oxidation states of Mn at the surface layers. This electronic and structural configuration of the as-synthesized particles is indirectly linked to strong adsorption pathways that promote the ORR on LaMnO3, and thus, it could prove to be a valuable design feature in the engineering of catalytic surfaces.

Journal article

Martinez-Casado R, Todorovi M, Mallia G, Harrison NM, Perez Ret al., 2019, First principles calculations on the stoichiometric and defective (101) anatase surface and upon hydrogen and H2Pc adsorption: The Influence of electronic exchange and correlation and of basis set approximations, Frontiers in Chemistry, Vol: 7, ISSN: 2296-2646

Anatase TiO2 provides photoactivity with high chemical stability at a reasonable cost. Different methods have been used to enhance its photocatalytic activity by creating band gap states through the introduction of oxygen vacancies, hydrogen impurities, or the adorption of phthalocyanines, which are usually employed as organic dyes in dye-sensitized solar cells. Predicting how these interactions affect the electronic structure of anatase requires an efficient and robust theory. In order to document the efficiency and accuracy of commonly used approaches we have considered two widely used implementations of density functional theory (DFT), namely the all-electron linear combination of atomic orbitals (AE–LCAO) and the pseudo-potential plane waves (PP–PW) approaches, to calculate the properties of the stoichiometric and defective anatase TiO2 (101) surface. Hybrid functionals, and in particular HSE, lead to a computed band gap in agreement with that measured by using UV adsorption spectroscopy. When using PBE+U, the gap is underestimated by 20 % but the computed position of defect induced gap states relative to the conduction band minimum (CBM) are found to be in good agreement with those calculated using hybrid functionals. These results allow us to conclude that hybrid functionals based on the use of AE–LCAO provide an efficient and robust approach for predicting trends in the band gap and the position of gap states in large model systems. We extend this analysis to surface adsorption and use the AE–LCAO approach with the hybrid functional HSED3 to study the adsorption of the phthalocyanine H2Pc on anatase (101). Our results suggest that H2Pc prefers to be adsorbed on the surface Ti5c rows of anatase (101), in agreement with that seen in recent STM experiments on rutile (110).

Journal article

Hilderbrand M, Abualnaja F, Makwana Z, Harrison Net al., 2019, Strain engineering of adsorbate self-assembly on graphene for band gap tuning, Journal of Physical Chemistry C, Vol: 123, Pages: 4475-4482, ISSN: 1932-7447

Recent interest in functionalized graphene has been motivated by the prospect of creating a two-dimensional semiconductor with a tunable band gap. Various approaches to band gap engineering have been made over the last decade, one of which is chemical functionalization. In this work, a predictive physical model of the self-assembly of halogenated carbene layers on graphene is suggested. Self-assembly of the adsorbed layer is found to be governed by a combination of the curvature of the graphene sheet, local distortions, as introduced by molecular adsorption, and short-range intermolecular repulsion. The thermodynamics of bidental covalent molecular adsorption and the resultant electronic structure are computed using density functional theory. It is predicted that a direct band gap is opened that is tunable by varying coverages and is dependent on the ripple amplitude. This provides a mechanism for the controlled engineering of graphene’s electronic structure and thus its use in semiconductor technologies.

Journal article

Rafols i Belles C, Selim S, Harrison NM, Ahmad EA, Kafizas Aet al., 2019, Beyond band bending in the WO3/BiVO4 heterojunction: insight from DFT and experiment, Sustainable Energy and Fuels, Vol: 3, Pages: 264-271, ISSN: 2398-4902

Heterojunction photocatalysts can significantly enhance the efficiency of photocatalytic water splitting. It is well known that the key to such improvements lies at the interfacial region where charge separation occurs. Understanding the origins of this interfacial enhancement can enable the design of better performing water splitting devices. Therefore, in this work, a novel theoretical–experimental approach is developed for the study of photocatalytic heterojunctions using the model system – WO3/BiVO4, where it has been shown that the quantum efficiency of water splitting can approach unity at certain wavelengths. Our photoelectrochemical measurements of this heterojunction show a significantly enhanced performance over its separate components when illuminated through the BiVO4 side but not the WO3 side. This is indicative of more efficient electron transfer (i.e. from BiVO4 to WO3) than hole transfer (i.e. from WO3 to BiVO4) across the junction. Our classical band bending model of this junction predicts noticeable interfacial barriers, but could not explain the reduced performance under back illumination. Our atomistic model was used to investigate the effect of interfacial reconstructions and chemical interactions on the electronic structure of the system. The model reveals a non-staggered valence band, in contrast to the staggered conduction band, due to strong hybridization of valence band orbitals in both materials across the interface. This non-staggered valence band does not provide an energetic driving force for charge separation for hole transfer (i.e. from WO3 to BiVO4 under back illumination). Hence, a significant improvement in performance is only observed under front illumination. This combined approach, using both experiment and theory, results in a more complete understanding of a heterojunction photocatalyst system and provides unique insight into the interfacial effects that arise when two semiconductor materials are brought together

Journal article

Martinez-Casado R, Mallia G, Harrison NM, Perez Ret al., 2018, First-principles study of the water adsorption on Anatase(101) as a function of the coverage, Journal of Physical Chemistry C, Vol: 122, Pages: 20736-20744, ISSN: 1932-7447

An understanding of the interaction of water with the anatase(101) surface is crucial for developing strategies to improve the efficiency of the photocatalytic reaction involved in solar water splitting. Despite a number of previous investigations, it is still not clear if water preferentially adsorbs in its molecular or dissociated form on anatase(101). With the aim of shedding some light on this controversial issue, we report the results of periodic screened-exchange density functional theory calculations of the dissociative, molecular, and mixed adsorption modes on the anatase(101) surface at various coverages. Our calculations support the suggestion that surface-adsorbed OH groups are present, which has been made on the basis of recently measured X-ray photoelectron spectroscopy, temperature-programmed desorption, and scanning tunneling microscopy data. It is also shown that the relative stability of water adsorption on anatase(101), at different configurations, can be understood in terms of a simple model based on the number and nature of the hydrogen bonds formed as well as the adsorbate-induced atomic displacements in the surface layers. These general conclusions are found to be insensitive to the specific choice of approximation for electronic exchange and correlation within the density functional theory. The simple model of water–anatase interactions presented here may be of wider validity in determining the geometry of water–oxide interfaces.

Journal article

Joshi GR, Cooper K, Zhong X, Cook AB, Ahmad EA, Harrison NM, Engelberg DL, Lindsay Ret al., 2018, Temporal evolution of sweet oilfield corrosion scale: Phases, morphologies, habits, and protection, Corrosion Science, Vol: 142, Pages: 110-118, ISSN: 0010-938X

Electrochemical measurements and substrate analysis have been employed to study the corrosion of iron in sweet solution (pH = 6.8, T = 80 °C) over a period of 288 h. Correlated with decreasing corrosion rate, diffraction, microscopy, and spectroscopy data reveal the evolution of adhered sweet corrosion scale. Initially, it is comprised of two phases, siderite and chukanovite, with the latter affording little substrate protection. Subsequently, as the scale becomes highly protective, siderite is the sole component. Notably, siderite crystals are concluded to display a somewhat unexpected habit, which may be a trigger for local breakdown of protective sweet scales.

Journal article

Fedotov G, Skorodumina IA, Burkert VD, Gothe RW, Hicks K, Mokeev V, Adhikari S, Armstrong WR, Avakian H, Ball J, Balossino I, Barion L, Bashkanov M, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brooks WK, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clary BA, Cole PL, Contalbrigo M, Cortes O, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Defurne M, Dear A, Djalali C, Dupre R, Egiyan H, El Fassi L, Eugenio P, Fersch R, Gavalian G, Ghandilyan Y, Gilfoyle GP, Girod FX, Golovatch E, Griffioen KA, Guo L, Hafidi K, Hakobyan H, Hanretty C, Harrison N, Hattawy M, Heddle D, Holtrop M, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Jo HS, Johnston S, Joosten S, Kabir ML, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim A, Kim W, Klein A, Klein FJ, Kubarovsky V, Kuleshov S, Lanza L, Lenisa P, Livingston K, MacGregor IJD, Markov N, McKinnon B, Mineeva T, Montgomery RA, Camacho CM, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Paolone M, Paremuzyan R, Park K, Pasyuk E, Pogorelko O, Price JW, Procureur S, Prok Y, Protopopescu D, Ripani M, Riser D, Ritchie BG, Rizzo A, Sabatie F, Salgado C, Schumacher RA, Sharabian YG, Smith GD, Sober D, Sokhan D, Sparveris N, Strakovsky II, Strauch S, Taiuti M, Tan JA, Tyler N, Ungaro M, Voskanyan H, Voutier E, Wei X, Wood MH, Zachariou N, Zhang J, Zhao ZWet al., 2018, Measurements of the gamma(upsilon)p -> p 'pi(+)pi(- )cross section with the CLAS detector for 0.4 GeV2 < Q(2) < 1.0 GeV2 and 1.3 GeV < W < 1.825 GeV, PHYSICAL REVIEW C, Vol: 98, ISSN: 2469-9985

Journal article

Bono J, Guo L, Raue BA, Adhikari S, Kunkel MC, Adhikari KP, Akbar Z, Amaryan MJ, Ball J, Barion L, Bashkanov M, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Brooks WK, Burkert VD, Cao F, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clary BA, Cole PL, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Vita R, Defurne M, Deur A, Diehl S, Djalali C, Dugger M, Egiyan H, El Alaoui A, El Fassi L, Eugenio P, Fedotov G, Filippi A, Fradi A, Gavalian G, Gevorgyan N, Ghandilyan Y, Girod FX, Glazier DI, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Hafidi K, Harrison N, Hattawy M, Heddle D, Hicks K, Holtrop M, Ilieva Y, Ireland DG, Isupov EL, Jo HS, Johnston S, Kabir ML, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim A, Kim W, Klein A, Klein FJ, Kubarovsky V, Lenisa P, Livingston K, MacGregor IJD, Markov N, McKinnon B, Mineeva T, Montgomery RA, Camacho CM, Niculescu G, Osipenko M, Ostrovidov AI, Paolone M, Paremuzyan R, Park K, Pasyuk E, Phelps W, Pogorelko O, Price JW, Prok Y, Protopopescu D, Ripani M, Rizzo A, Rosner G, Sabatie F, Salgado C, Schumacher RA, Sharabian Y, Skorodumina I, Smith GD, Sokhan D, Sparveris N, Stepanyan S, Strakovsky II, Strauch S, Taiuti M, Tan JA, Ungaro M, Voskanyan H, Voutier E, Wang R, Wei X, Wood MH, Zachariou N, Zana L, Zhang J, Zhao ZWet al., 2018, First measurement of Xi(-) polarization in photoproduction, PHYSICS LETTERS B, Vol: 783, Pages: 280-286, ISSN: 0370-2693

Journal article

Kunkel MC, Amaryan MJ, Strakovsky II, Ritman J, Goldstein GR, Adhikari KP, Adhikari S, Avakian H, Ball J, Balossino I, Barion L, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brooks WK, Bultmann S, Burkert VD, Cao F, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clark L, Cole PL, Contalbrigo M, Cortes O, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Degtyarenko P, Defurne M, Deur A, Djalali C, Dugger M, Dupre R, Egiyan H, El Alaoui A, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fersch R, Filippi A, Fradi A, Gavalian G, Ghandilyan Y, Ghosh S, Gilfoyle GP, Giovanetti KL, Girod FX, Glazier D, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Guo L, Guidal M, Hafidi K, Hakobyan H, Harrison N, Hattawy M, Hicks K, Holtrop M, Hyde CE, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Joo K, Kabir ML, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim A, Kim W, Klein A, Klein F, Kubarovsky V, Kuhn SE, Laget JM, Lanza L, Lenisai P, Lersch D, Livingston K, Macgregor IJD, Markov N, Njencheu GM, Mckinnon B, Mineeva T, Mokeev V, Montgomery RA, Movsisyani A, Camacho CM, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Ostrovidovi A, Paolone M, Park K, Pasyuk E, Payette D, Phelps W, Pogorelko O, Poudel J, Price JW, Procureur S, Prok Y, Protopopescu D, Ripani M, Ritchie BG, Rizzo A, Rosner G, Roy A, Sabatie F, Salgado C, Schadmand S, Schumacher RA, Sharabian YG, Skorodumina I, Stepanyan S, Sokhan D, Sober D, Sparveris N, Strauch S, Taiuti M, Tan JA, Ungaro M, Voskanyan H, Voutier E, Watts DP, Weinstein L, Wei X, Weygand DP, Zachariou N, Zhang J, Zhao ZWet al., 2018, Exclusive photoproduction of pi degrees up to large values of Mandelstam variables s, t, and u with CLAS, PHYSICAL REVIEW C, Vol: 98, ISSN: 2469-9985

Journal article

Jawalkar S, Koirala S, Avakian H, Bosted P, Griffioen KA, Keith C, Kuhn SE, Adhikari KP, Adhikari S, Adikaram D, Akbar Z, Amaryan MJ, Pereira SA, Ball J, Baltzell NA, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brock J, Brooks WK, Bultmann S, Burkert VD, Cao FT, Carlin C, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clark L, Colaneri L, Cole PL, Contalbrigo M, Cortes O, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Defurne M, Deur A, Djalali C, Ddoge G, Dupre R, Egiyan H, El Alaoui A, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fegan S, Fersch R, Filippi A, Fleming JA, Forest TA, Fradi A, Garcon M, Ghandilyan Y, Gilfoyle GP, Giovanetti KL, Girod FX, Gleason C, Gohn W, Golovatch E, Gothe RW, Guidal M, Guler N, Guo L, Hakobyan H, Hanretty C, Harrison N, Hattawy M, Heddle D, Hicks K, Hollis G, Holtrop M, Hughes SM, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Jiang H, Joo K, Joosten S, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim A, Kim W, Klein A, Klein FJ, Kubarovsky V, Kuleshov SV, Lanza L, Lenisa P, Livingston K, Lu HY, MacGregor IJD, Markov N, Mayer M, McCracken ME, McKinnon B, Meyer CA, Mineeva T, Mirazita M, Mokeev V, Montgomery RA, Movsisyan A, Camacho CM, Nadel-Turonski P, Net LA, Niccolai S, Niculescu G, Niculescu I, Osipenko M, Ostrovidov AI, Paremuzyan R, Park K, Pasyuk E, Phelps E, Phelps W, Pierce J, Pisano S, Pogorelko O, Price JW, Prok Y, Protopopescu D, Raue BA, Ripani M, Riser D, Rizzo A, Rosner G, Rossi P, Sabatie F, Salgado C, Schumacher RA, Seder E, Sharabian YG, Simonyan A, Skorodumina I, Smith GD, Sober DI, Sokhan D, Sparveris N, Stankovic I, Strauch S, Taiuti M, Ungaro M, Voskanyan H, Voutier E, Walford NK, Watts DP, Wei X, Weinstein LB, Wood MH, Zachariou N, Zhang J, Zhao ZWet al., 2018, Semi-inclusive pi(0) target and beam-target asymmetries from 6 GeV electron scattering with CLAS, PHYSICS LETTERS B, Vol: 782, Pages: 662-667, ISSN: 0370-2693

Journal article

Chetry T, Hicks K, Compton N, Sargsian M, Adhikari S, Ball J, Balossino I, Barion L, Battaglieri M, Batourine V, Bedlinskiy I, Biselli AS, Boiarinov S, Briscoe WJ, Brooks WK, Burkert VD, Carman DS, Celentano A, Charles G, Ciullo G, Clark L, Clary BA, Cole PL, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Deur A, Djalali C, Dupre R, El Alaoui A, El Fassi L, Eugenio P, Fedotov G, Fersch R, Filippi A, Gavalian G, Ghandilyan Y, Giovanetti KL, Girod FX, Golovatch E, Gothe RW, Griffioen KA, Guo L, Hafidi K, Harrison N, Hattawy M, Holtrop M, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Johnston S, Kabir ML, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim A, Kim W, Klein FJ, Kubarovsky V, Lanza L, Lenisa P, Livingston K, MacGregor IJD, Markov N, McKinnon B, Mokeev V, Movsisyan A, Camacho CM, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Ostrovidov AI, Paolone M, Paremuzyan R, Park K, Pasyuk E, Phelps W, Pogorelko O, Price JW, Prok Y, Ripani M, Riser D, Ritchie BG, Rizzo A, Rosner G, Salgado C, Schumacher RA, Skorodumina I, Smith GD, Sober DI, Sokhan D, Sparveris N, Stepanyan S, Strakovsky II, Strauch S, Taiuti M, Tan JA, Ungaro M, Voskanyan H, Voutier E, Weinstein LB, Wood MH, Zachariou N, Zhang J, Zhao ZWet al., 2018, Differential cross section for gamma d -> omega d using CLAS at Jefferson Lab, PHYSICS LETTERS B, Vol: 782, Pages: 646-651, ISSN: 0370-2693

Journal article

Park K, Guidal M, Gothe RW, Pire B, Semenov-Tian-Shansky K, Laget J-M, Adhikari KP, Adhikari S, Akbar Z, Avakian H, Ball J, Balossino I, Baltzell NA, Barion L, Battaglieri M, Bedlinskiy I, Biselli AS, Briscoe WJ, Brooks WK, Burkert VD, Cao FT, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clark L, Cole PL, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Defurne M, Deur A, Djalali C, Dupre R, Egiyan H, El Alaoui A, El Fassi L, Elouadrhiri L, Eugenio P, Fedotov G, Fersch R, Filippi A, Garcon M, Ghandilyan Y, Gilfoyle GP, Girod FX, Golovatch E, Griffioen KA, Guo L, Hafidi K, Hakobyan H, Hanretty C, Harrison N, Hattawy M, Heddle D, Hicks K, Holtrop M, Hyde CE, Ilieva Y, Ireland DG, Ishkhanov BS, Isupov EL, Jenkins D, Johnston S, Joo K, Kabir ML, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim W, Klein FJ, Kubarovsky V, Kuhn SE, Lanza L, Livingston K, MacGregor IJD, Markov N, McKinnon B, Mirazita M, Mokeev V, Montgomery RA, Camacho CM, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Paolone M, Paremuzyan R, Pasyuk E, Phelps W, Pogorelko O, Poudel J, Price JW, Prok Y, Protopopescu D, Ripani M, Rizzo A, Rossi P, Sabatie F, Salgado C, Schumacher RA, Sharabian Y, Skorodumina I, Smith GD, Sokhan D, Sparveris N, Stepanyan S, Strakovsky II, Strauch S, Taiuti M, Tan JA, Ungaro M, Voskanyan H, Voutier E, Wei X, Zachariou N, Zhang Jet al., 2018, Hard exclusive pion electroproduction at backward angles with CLAS, PHYSICS LETTERS B, Vol: 780, Pages: 340-345, ISSN: 0370-2693

Journal article

Chang V, Noakes TCQ, Harrison N, 2018, Work function and quantum efficiency study of metal oxide thin films on Ag(100), Physical Review B, Vol: 97, ISSN: 2469-9950

Increasing the quantum efficiency (QE) of metal photocathodes is in the design and development of photocathodes for free-electron laser applications. The growth of metal oxide thin films on certain metal surfaces has previously been shown to reduce the work function (WF). Using a photoemission model B. Camino [Comput. Mater. Sci. 122, 331 (2016)CMMSEM0927-025610.1016/j.commatsci.2016.05.025] based on the three-step model combined with density functional theory calculations we predict that the growth of a finite number of MgO(100) or BaO(100) layers on the Ag(100) surface increases significantly the QE compared with the clean Ag(100) surface for a photon energy of 4.7 eV. Different mechanisms for affecting the QE are identified for the different metal oxide thin films. The addition of MgO(100) increases the QE due to the reduction of the WF and the direct excitation of electrons from the Ag surface to the MgO conduction band. For BaO(100) thin films, an additional mechanism is in operation as the oxide film also photoemits at this energy. We also note that a significant increase in the QE for photons with an energy of a few eV above the WF is achieved due to an increase in the inelastic mean-free path of the electrons.

Journal article

Savazzi F, Risplendi F, Mallia G, Harrison NM, Cicero Get al., 2018, Unravelling some of the structure-property relationships in graphene oxide at low degree of oxidation, Journal of Physical Chemistry Letters, Vol: 9, Pages: 1746-1749, ISSN: 1948-7185

Graphene oxide (GO) is a versatile 2D material whose properties can be tuned by changing the type and concentration of oxygen-containing functional groups attached to its surface. However, a detailed knowledge of the dependence of the chemo/physical features of this material on its chemical composition is largely unknown. We combine classical molecular dynamics and density functional theory simulations to predict the structural and electronic properties of GO at low degree of oxidation and suggest a revision of the Lerf–Klinowski model. We find that layer deformation is larger for samples containing high concentrations of epoxy groups and that correspondingly the band gap increases. Targeted chemical modification of the GO surface appears to be an effective route to tailor the electronic properties of the monolayer for given applications. Our simulations also show that the chemical shift of the C-1s XPS peak allows one to unambiguously characterize GO composition, resolving the peak attribution uncertainty often encountered in experiments.

Journal article

Harrison N, 2018, Computational characterisation of catalysts in reactive environments: Phase stability, surface compostion, structure and reaction sites, 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727

Conference paper

Chandavar S, Goetz JT, Hicks K, Keller D, Kunkel MC, Paolone M, Weygand DP, Adhikari KP, Adhikari S, Akbar Z, Ball J, Balossino I, Barion L, Bashkanov M, Battaglieri M, Bedlinskiy I, Biselli AS, Briscoe WJ, Brooks WK, Burkert VD, Cao F, Carman DS, Celentano A, Charles G, Chetry T, Ciullo G, Clark L, Cole PL, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Defurne M, Deur A, Djalali C, Dupre R, Egiyan H, El Alaoui A, El Fassi L, Eugenio P, Fedotov G, Filippi A, Fradi A, Gavalian G, Ghandilyan Y, Gilfoyle GP, Girod FX, Glazier DI, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Guidal M, Guo L, Hafidi K, Hakobyan H, Hanretty C, Harrison N, Hattawy M, Heddle D, Holtrop M, Ilieva Y, Ireland DG, Isupov EL, Jenkins D, Johnston S, Joo K, Joosten S, Kabir ML, Khachatryan G, Khachatryan M, Khandaker M, Kim W, Klein A, Klein FJ, Kubarovsky V, Lanza L, Lenisa P, Livingston K, MacGregor IJD, Markov N, McCracken ME, McKinnon B, Meyer CA, Mineeva T, Mokeev V, Movsisyan A, Camacho CM, Nadel-Turonski P, Niccolai S, Niculescu G, Osipenko M, Ostrovidov AI, Paremuzyan R, Park K, Pasyuk E, Phelps W, Pogorelko O, Price JW, Prok Y, Protopopescu D, Raue BA, Ripani M, Riser D, Ritchie BG, Rizzo A, Rosner G, Sabatie F, Salgado C, Schumacher RA, Sharabian YG, Simonyan A, Skorodumina I, Sokhan D, Smith GD, Sparveris N, Stepanyan S, Strakovsky II, Strauch S, Ungaro M, Voutier E, Wei X, Zachariou N, Zhang J, Zhao ZWet al., 2018, Double K-S(0) photoproduction off the proton at CLAS, PHYSICAL REVIEW C, Vol: 97, ISSN: 2469-9985

Journal article

Adhikari KP, Deur A, El Fassi L, Kang H, Kuhn SE, Ripani M, Slifer K, Zheng X, Adhikari S, Akbar Z, Amaryan MJ, Avakian H, Ball J, Balossino I, Barion L, Battaglieri M, Bedlinskiy I, Biselli AS, Bosted P, Briscoe WJ, Brock J, Bultmann S, Burkert VD, Cao FT, Carlin C, Carman DS, Celentano A, Charles G, Chen J-P, Chetry T, Choi S, Ciullo G, Clark L, Cole PL, Contalbrigo M, Crede V, D'Angelo A, Dashyan N, De Vita R, De Sanctis E, Defurne M, Djalali C, Dodge GE, Drozdov V, Dupre R, Egiyan H, El Alaoui A, Elouadrhiri L, Eugenio P, Fedotov G, Filippi A, Ghandilyan Y, Gilfoyle GP, Golovatch E, Gothe RW, Griffioen KA, Guidal M, Guler N, Guo L, Hafidi K, Hakobyan H, Hanretty C, Harrison N, Hattawy M, Heddle D, Hicks K, Holtrop M, Hyde CE, Ilieva Y, Ireland DG, Isupov EL, Jenkins D, Jo HS, Johnston SC, Joo K, Joosten S, Kabir ML, Keith CD, Keller D, Khachatryan G, Khachatryan M, Khandaker M, Kim W, Klein A, Klein FJ, Konczykowski P, Kovacs K, Kubarovsky V, Lanza L, Lenisa P, Livingston K, Long E, MacGregor IJD, Markov N, Mayer M, McKinnon B, Meekins DG, Meyer CA, Mineeva T, Mirazita M, Mokeev V, Movsisyan A, Camacho CM, Nadel-Turonski P, Niculescu G, Niccolai S, Osipenko M, Ostrovidov AI, Paolone M, Pappalardo L, Paremuzyan R, Park K, Pasyuk E, Payette D, Phelps W, Phillips SK, Pierce J, Pogorelko O, Poudel J, Price JW, Prok Y, Protopopescu D, Raue BA, Rizzo A, Rosner G, Rossi P, Sabatie F, Salgado C, Schumacher RA, Sharabian YG, Shigeyuki T, Simonyan A, Skorodumina I, Smith GD, Sparveris N, Sokhan D, Stepanyan S, Strakovsky II, Strauch S, Sulkosky V, Taiuti M, Tan JA, Ungaro M, Voutier E, Wei X, Weinstein LB, Zhang J, Zhao ZWet al., 2018, Measurement of the Q(2) Dependence of the Deuteron Spin Structure Function g(1) and its Moments at Low Q(2) with CLAS, PHYSICAL REVIEW LETTERS, Vol: 120, ISSN: 0031-9007

Journal article

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