Background:
Summary of Methods Used
Simple Example:
Theory
The Vibrations
Research Topics:
Fatty Acid Methyl Esters (FAMEs)
| School of Chemistry |
A Brief Summary of the Methods I use to do My Research
Most of my work is achieved through the use of the Gaussian 98 suite of programmes [2]. I use both Gaussview and gOpenMol [3,4] to build and display molecules, their vibrational modes and various surfaces. As described earlier, I will also be using Chime to display various aspects of my work here.
Throughout history, chemistry has always been an experimental subject, but in the past twenty years or so, powerful computers have made the theoretical prediction of chemical properties possible. The cost of computers has fallen steadily and this, together with increasingly sophisticated software, encouraged theoretical chemists to use computational techniques. Gradually, other branches of chemistry i.e. physical, organic and inorganic chemists, have begun to use standard software packages in much the same way as any other piece of experimental apparatus. Like I.R. or N.M.R. spectrometers, the software may be treated almost like 'black boxes' but the best results come from having an understanding of the strengths and weaknesses of the techniques.
There are three main levels of theory at which calculations can be performed, these are;
- Molecular mechanics
- Semi-empirical techniques
- Ab initio / Density Functional Theory (DFT)
I almost always use DFT methods to calculate the properties of the molecules I am interested in. Most of my calculations so far have been at the B3LYP level of theory with the 6-31G(d) basis set.
You'll be relieved to know that I'm not going to say anything more about the maths, there are plenty of other sites that can explain the theoretical background of DFT in a much better way than I can. Three of these are;
Introduction to Computational Chemistry by David Young
NIH Guide to Molecular Modelling
I use the results from my calculations to help interpret Raman Spectra but it's probably sensible at this point to make it quite clear that I don't do Raman experiments myself. I know the theory behind the technique and I have been in the lab. when spectra have been aquired, but I don't know how to set-up the equipment or how to make it work!
As a result of this - there is no point in asking me anything to do with lasers and signals and things like that, I don't have a clue.
