When I did my graduate work in quantum chemistry, doing a calculation on something the size of, say, hexatriene was a huge deal. In those days, the calculations were limited to people with expertise and perseverance - and a lot of patience. GUI? We didn't need no stinkin' GUI. We set up input files by hand, even had to work out the Cartesian coordinates of the atoms on a hand calculator. Those times have changed.
A combination of factors helped to make quantum mechanical calculations accessible to a wider range of users:
- Computers got faster. These calculations take a long time, but computers today are around 1,000-10,000x faster than when I was in grad school.
- Modeling methods got faster. Besides simply optimizing software performance, there were breakthrough approaches like density functional theory (DFT), which delivered reliable results with less CPU time.
- Graphical User Interfaces (GUIs). Yes, it turns out that we do need those stinkin' GUIs. It's just not feasible to set up calculations for anything more than around a dozen atoms without a sketcher.
DFT has done particularly well over the past 10 years or so. On top of everything else, the methods have been extended to include systems with periodic boundary conditions, so chemists have started getting into solid state calculations. With this approach you can study heterogeneous catalysis on an extended (periodic) surface; predict crystal structures; or calculate elastic constants. Searching ACS for "density functional theory" shows a staggering increase from 37 publications in1989 to almost 4000 so far this year.
Among some interesting research directions are those to compute solid-state spectra. This includes NMR, Raman, and EELS (electron energy loss spectra), all of which are part of the drive to make DFT more relevant by connecting theory with experiment. Raman is used, for example, to characterize reactions in situ. NMR can be used to discriminate among crystal polymorphs. EELS has "enabled detailed measurements of the atomic and electronic properties of single columns of atoms, and in a few cases, of single atoms." Earlier this year, there was even a workshop sponsored by the Oxford University Department of Materials to promote these computational approaches specifically to the experimental community. This combination of theory and experiment facilitates the identification of unknown compounds; the elucidation of reaction mechanisms; and the characterization of molecular & crystal structure.
One of the most gratifying measures of success is the appearance of articles not directed at other specialists. NewScientist recently ran an article about using DFT to predict crystal structure entirely from first principle - a sort of DFT for the common man type article.
As a developer and practitioner of DFT, I'm really pleased to see how far the awareness of theory in general and DFT in particular has spread. Who knows: someday there may even be an iPhone application for DFT.