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Computer Modeling

The unsung champions in nanotechnology are the many theorists, mathematicians, physicists, and computer modelers who strive endlessly to gain insight into the nanoscale world.  For every experiment that results in recorded empirical data, it's vitally important for scientists and engineers to see how that data fits in with their theory and models.  If there is a serious deviation between the two, it could mean there are problems with the experiment, the model, or both!

Theorists don't have it easy.  They work in an abstract world of numbers and graphs.  The inherent challenge of theory in the nanoscale is that scientists must work in an intermediate world between quantum theory (that governs atoms) and bulk theory (which governs macroscopic materials).  Most nanoscale structures and devices are at least 3-20 nm across.  In this range, it isn't appropriate to model a semiconductor nanowire, for instance, as a cylindrical quantum well of infinite length.  That would be the bulk model.  The thing is, a nanowire that is only 10 nm across is only 100 atoms in diameter.  At this scale, you can't use bulk values to extract the wire's electronic properties.  Instead, you'll need to take into account the fact that in the nanoscale, atoms (and their lattice positions) are extremely important.

To make things worse, molecular theory is not a complete science.  In fact, it is impossible to fully solve a two-hydrogen (the standard H2 gas molecule) system without having to make serious sacrifices in the model you choose to use.  So taking a fully atomistic approach won't work either.

In the end, successful theories have mixed the two worlds of atoms and bulk systems of atoms in order to elucidate the nature of many nano structures like quantum dots and wires.  These calculations are very extensive. If you did them by hand it would take months to complete.  Luckily, simple calculations with results within a few percent-error of more complex calculations only require about 30 minutes to an hour.  Serious calculations can require several hours at once.

These results are very important because our current synthesis methods are not that precise.  We often end up with a spread of diameters when making nanowires, so it's extremely difficult to analyze the empirical results.  This is why theory is important.  It opens windows of knowledge that were previously closed to us.  Though often the theory and experimentation don't match up completely, we can't do one without having the other.  It's a dynamic balance that continually seeks to re-adjust itself as we progress with our scientific endeavors.