AB INITIO MOLECULAR DYNAMICS - Density Functional Theory - page 193

AB INITIO MOLECULAR DYNAMICS
An unavoidable characteristic of the materials that surround us is that their
atoms are in constant motion. There are a large set of topics for which knowing
how the atoms in a material move as a function of time is a prerequisite for
describing some property of practical interest. In this chapter, we explore
the methods of molecular dynamics (MD), a set of computational tools that
makes it possible to follow the trajectories of moving atoms. We begin in
Section 9.1 by stepping back from quantum mechanics temporarily and
describing how MD simulations are performed using classical mechanics.
This detour introduces several concepts that are critical in using MD within
DFT calculations. Section 9.2 introduces the methods that can be used to per-
form MD simulations using information derived from DFT calculations.
Section 9.3 gives two examples of using ab initio MD, one involving the
generation of disordered bulk materials and another in which MD is used to
explore complicated energy surfaces.
9.1 CLASSICAL MOLECULAR DYNAMICS
9.1.1 Molecular Dynamics with Constant Energy
To understand the main ideas that define ab initio MD, it is useful to first review
some concepts from classical mechanics. Classical MD is a well-developed
approach that is widely used in many types of computational chemistry and