Molecular
calculations of NO, NO2 and Anisole
Jen Schauer and Liem Nguyen
Introduction:
The reactivity and stability of a molecule depend
mainly on its electronic structure and properties, which include the
locations of electrons, available energy levels, vibrational
frequencies, dipole moments and UV- Visible spectrum. These properties
can be modeled mathematically and computed using computer programs. The
calculations are complicated and could require a great amount of time
for large molecules. So far ab initio is the best theory for these
quantum calculations.
The three molecules of interest in this experiment
were NO, NO2 and anisole. The calculation formulated each molecule with
a basis set, which is a combination of normalized wavefunctions. Some
basis sets commonly chosen are 321G, 631G and DZV (Double Zeta
Valence), which were used in the experiment. With the specific basis
set, optimized geometry for the molecule was determined and other
properties such as HOMO orbitals, vibrational frequencies, bond lengths
and angles were obtained. Finally, using surface energy calculations, a
bond strech and potential energy was plotted and UV- visible spectrum
of each molecule was obtained and compared to literature values.
Experimental:
In WebMO Job Manager, the molecule (NO, NO2 or
anisole) was built and ran an intitial geometry optimization with
either basic set AM1 or STO3G. An input file was generated WXMacMolPlt
from the first calculation to run other geometry optimization of higher
basic set (3-21G, 6-31G and DZV) in the compiler GTK Gamess. Once the
geometry optimization was obtained, vibrational energy calculations
were done. In Jmol the optimized molecule with bond lengths and angles
were displayed for each level theory and export to a webpage template.
The HOMO orbital of each molecule as the animation of main vibrational
frequencies were also exported using Jmol.
Surface energy calculations were run to examine the
change in potential energy due to bond stretching for each level
theory. In Igor, a graph of potential energy vs bond stretching was
plotted for each basis set and compared.
Click to see three molecular calculations: NO,
NO2,
and anisole
References:
1 http://cccbdb.nist.gov/. Vibrations. Experimental
vibrational data for a given species. NO,NO2.
2 http://cccbdb.nist.gov/ . Geometries.
Experimental geometry data for a given species. NO,NO2.
3 http://riodb01.ibase.aist.go.jp. Spetcra Database
For Organic Compound. Anisole IR
Spectrum.