## The H3 linear cluster

In this section you will calculate the wavefunction of a H3 cluster by loading a CRYSTAL input file: H3_linear.inp

Exercise 1: Start DLVisualize and run a CRYSTAL calculation:

> Calculate->CRYSTAL->Run SCF Input file
> Click on Browse
> Select H3.inp
> Select OK
> Select OK

The Job List panel will open automatically and look something like this;

Select the job and the status line should report "Job has completed" - like this;

> Click on Recover Files.

A model of H3 should have appeared in the DLV 3DView window.

A second window will open displaying the output from the CRYSTAL calculation (the LogFile).

It should look something like H3_linear.out

Take some time to read through the output in order to answer to the following questions.

Questions:

1. What are the H-H distances?
   Compare with the H-H distance in the H2 molecule.
2. Did you use the same hamiltonian/method adopted in the calculation of the hydrogen atom and molecule?
3. What is the energy of the H3 cluster in Hartree?
   In the output, the energy is given in atomic unit (Hartree).
   Convert the energy in eV and in J.
   Compare this energy with the exact energy of three isolated hydrogen atoms. Which conclusion can be drawn?
4. What are the energies of the molecular orbitals?
   Hints: Look for the string "FINAL EIGENVALUES (A.U.)" at end of the output.
   The energies are given in atomic unit (Hartree). Convert in eV and in J.
   Compare the energies of the molecular orbitals of H3 with H2.

Optional questions::

1. Is it possible to identify a non-bonding molecular orbital?
   Compare the eigenvalues with the energy of the occupied atomic orbital of hydrogen atom.

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