Chemistry Reference
In-Depth Information
yourself in a research setting or so you can interact knowledgeably with
collaborators who use these methods.
An analogy related to cars may be useful here. Before you learned how to
drive, it was presumably clear to you that you can accomplish many useful
things with the aid of a car. For you to use a car, it is important to understand
the basic concepts that control cars (you need to put fuel in the car regularly,
you need to follow basic traffic laws, etc.) and spend time actually driving a car
in a variety of road conditions. You do not, however, need to know every detail
of how fuel injectors work, how to construct a radiator system that efficiently
cools an engine, or any of the other myriad of details that are required if you
were going to actually build a car. Many of these details may be important
if you plan on undertaking some especially difficult car-related project such
as, say, driving yourself across Antarctica, but you can make it across town
to a friend's house and back without understanding them.
With this topic, we hope you can learn to “drive across town” when doing
your own calculations with a DFT package or when interpreting other people's
calculations as they relate to physical questions of interest to you. If you are
interested in “building a better car” by advancing the cutting edge of
method development in this area, then we applaud your enthusiasm. You
should continue reading this chapter to find at least one surefire project that
could win you a Nobel prize, then delve into the topics listed in the Further
Reading at the end of the chapter.
At the end of most chapters we have given a series of exercises, most of
which involve actually doing calculations using the ideas described in the
chapter. Your knowledge and ability will grow most rapidly by doing rather
than by simply reading, so we strongly recommend doing as many of the exer-
cises as you can in the time available to you.
1.2 EXAMPLES OF DFT IN ACTION
Before we even define what density functional theory is, it is useful to relate a
few vignettes of how it has been used in several scientific fields. We have
chosen three examples from three quite different areas of science from the
thousands of articles that have been published using these methods. These
specific examples have been selected because they show how DFT calcu-
lations have been used to make important contributions to a diverse range of
compelling scientific questions, generating information that would be essen-
tially impossible to determine through experiments.
1.2.1 Ammonia Synthesis by Heterogeneous Catalysis
Our first example involves an industrial process of immense importance: the
catalytic synthesis of ammonia (NH
3
). Ammonia is a central component of
