Molecular Orbital calculations of Oxygen, Monofluoroamine, and M-Xylene
Jessica McGowan and Wesley Morioka
Abstract
Molecules can be geometrically
optimized with quantum calculations
to find their: bond lengths, highest occupied molecular
orbital, lowest
unoccupied molecular orbital, electrostatic potential, and
partial atomic
charges. Data collected for each molecule was done on the ab
initio
theory, which calculates the best level of theory. The calculations come from the best level of theory of 6-21G,
6-31G and DZV.1
The level of theory are also able to predict the dipole moments
occurring with in
the molecule and an absorbance spectra of transitional
energies. These quantum
calculations were performed on Oxygen, Monofluoroamine, and M-xylene.
The basis sets of AM1 generate the best level of theory for
the dipole moment
of Monofluoroamine, and the basis set of DZV to determine the
best level of
theory for the vibrational frequencies.
Introduction
With present technological
advancements have been made and computers can predict quantum
calculations in a
more simplified way
compared to doing the calculations with paper and pencil, even
though it is still feasible to do the calculations be hand. This
is beneficial
for calculations of larger molecules. Technology programs such
as, Avogadro,
MacMolPlt, Jmol, and GAMESS help aid with predicting
properties of molecules
without having to do long calculations. The properties that
these programs
assist with are: optimized geometry, the molecular dipole
moment, vibrational
frequencies, an absorption spectrum of transitional energies,
and the molecular
orbital structure of sigma and pi bonds with in the highest
occupied and lowest
unoccupied states.
From the entire
potential basis sets used the best results came from DZV. The
DZV basis set had
the most ideal calculation, especially for our larger molecule
m-xylene. DZV
was the best theory for our dipole moment of the polar
molecule
monofluoroamine, vibrational frequencies for the diatomic
molecule oxygen and
the motions associated with the vibrational spectrum.
When
using the programs to calculate the data there was some
experimental error
giving 6% in the bond length and 13.6% error in the
vibrational frequency of
oxygen. Another source of error stems from the dipole moment
in monofluoroamine
of 0.19%. A major benefit of doing computational data with the
computer is it
saves time in calculations for larger molecules. A
disadvantage for doing the
computations with computers is that the data is not consistent
with each other
and more data basis sets are needed to obtain improved
results.
References