Introduction: Multiple software programs were used in this experiment to determine dipole moments, bond lengths and angles, molecular vibrations, and potential energy of the molecule. The variational principle was used to find the energy by approximations with sums of trial wavefunctions. These calculations are used to determine the structure of the molecules, and the software programs used are relatively new. Prior to the software used, these calculations had to be done by hand, so using the software saves a relatively good amount of time. The most accurate program used was the Ab initio. As the basis set increased, the accuracy increased as well. These basis sets were as follows:  AM1/PM3, 6-21G, 6-31G, and DZV.

The program Avogadro was used to build the molecules that were designated to the group which were: CS, Formaldehyde, and 2-Fluorobiphenyl. These files were then saved as a .xyz document. The xxMacMolPlt was then used to generate the geometry optimizations for the molecules. These files were then submitted to GAMESS. The GamessQ was then used to check the log files to make sure the calculations were completed correctly. The atomic orbitals were then recorded. Files were then created for the ab initio geometry using the wxMacMolt to create the files. Jmol was then used to compare the geometries from the calculations. The .inp files were created for vibrational frequencies and were calculated using the GamessQ software. Use texteditor to find the units on the dipole, and record these numbers. Allow calculations to be run on the ab initio geometries for the other molecules for the 6-21G, 6-31G, and DZV basis sets for the diatomic molecule as well as the aromatic molecule. Use Jmol to visualize the vibrations and compare the calculated energies with those observed in the experimental IR spectra.

For CS and CH2O, the calculated dipole moments became closer to the actual dipole moments as the basis set approached DZV. For CS, there is a large jump from the 6-31G basis set to DZV. Better dipole moments were found for CS by redoing the calculations with different polarization functions. The best dipole moments were given by setting the number of D heavy atoms to 3 and the number of F heavy atoms to 1. Changing the light atom polarization function did not affect the dipole moment. The best result was found to be 1.504180 D. For CH2O, there was a steady upward trend as the basis set increased. With the best basis set used, DZV, the dipole moment was less than 1/10th of a Debye away from the actual dipole moment. The 2-fluorobiphenyl actual dipole moment was not found. However, there was a steady upward trend as the effectiveness of the basis set increased.

UV-Visible spectrum was not found for 2-fluorobiphenyl, so both Biphenyl and Fluorbenzene UV Visible Spectrum are shown below.

Biphenyl UV-Visible Spectrum

Fluorobenzene UV-Visible Spectrum