Authors: Brandon Brummeyer and Laura Hagen

Abstract
The Theory of Quantum Mechanics allows us to predict physical properties of molecules using complicated mathematics. Using advanced programs, we calculated some physical properties of three different molecules (Fluorine, Sulfur Dioxide, and m-dichlorobenzene). We used different calculation theories to obtain different comparative results of selective physical properties like the geometry, vibrational energies, and different orbitals and compared them to actual values obtained from NIST.

Introduction
Quantum mechanics is a mathematical model to aid in the description of atoms and molecules. There exists numerous theories in calculating the physical properties of atoms and molecules. A good model frequently used is the variational method, which does subsequent steps of calculations in order to find the best calculation that produces the lowest potential energy to describe the atom or molecule. In this experiment, the physical properties of the molecules diatomic fluorine, sulfur dioxide, and m-dichlorobenzene were calculated using the variational method. Within the variational method, a molecular mechanics calculation was performed followed by four basis sets (AM1, 6-21G, 6-31G and DZV). The initial calculation used was the standard molecular mechanics performed using Avogadro software. This is based on simplistic mechanics and electrostatics. These results were used to perform a semi-empirical calculation using Hamiltionians called AM1 in the mxMacMolPlt input file maker software. The input file was sent to Gamess using the queue software GamessQ to perform the calculation. This input file generation process was repeated for the 6-21G, 6-31G and DZV calculations which are ab initio theories. Each output file showed numerical results for certain physical properties such as dipole moments, optimized geometries, vibrational frequency energies and predicted UV-Vis spectrum values. Other specific properties were calculated for each of the molecules. In the Jmol software, the output data was loaded in order to create visual images based on the numerical values in order to create orbital maps, vibrational frequency animations, geometry images and electrostatic potential maps. Using Jmol and Seamonkey software, a collaborative website was created to display the results of the calculations with comparisons to the actual values acquired from the NIST website.

 Conclusion
Atoms and molecules can be characterized using calculation models. Different theories of calculations can be used to successfully describe the actual parameters found at NIST. Geometric properties, electrostatic properties, vibrational frequency energies and molecular orbitals were calculated using AM1, 6-21G, 6-31G and DZV basis sets. Some of these basis sets provided useful results while others had results far away from the actual values. The DZV basis set is supposed to be the highest theory in that is uses the subsequent results of the other three basis sets. The results of the experiments showed that sometimes the DZV calculations provided accurate results and other times the 6-21G had accurate results to describe the molecules. For diatomic fluorine all of the basis sets were able to describe the physical properties accurately because it is a simple molecule. The m-dichlorobenzene molecule is large and the most accurate results were from the DZV basis set.  The larger the molecule, the more complicated the calculations need to be in order to accurately describe the molecules physical properties and therefore becomes difficult to predict useful information. Large molecules such as proteins are very difficult to describe even with ab initio calculations.

References:
1. National Insititue of Standards and Technology. US Department of Commerce. http://www.nist.gov/
2. Gutow, Jonathan. Dr. Gutow's Tools for Authoring Jmol Web Pages. 13 Jan. 2014. https://cms.gutow.uwosh.edu/gutow/Jmol_Web_Page_Maker/Export_to_web_tutorial.shtml.
3. Mihalick, Jennifer; Gutow, Jonathan. Molecular Orbital (MO) Calculations. UW Oshkosh, Oshkosh, WI. Feb. 2014.

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      ...adding m-Dichlorobenzene.spt