| Summary: | Molecular dynamics is a technique in which the
trajectories of a group of particles are calculated as a
function of time by integrating the equations of motion. In
this thesis we study the use of molecular dynamics for atoms
in a crystal.
A model is introduced which describes interactions of a
physical system with an external heat reservoir in molecular
dynamics simulations. This is accomplished by the addition
of a "virtual variable" to the Hamiltonian which is used to
scale time. Aspects of this model are discussed and
examples are presented for a simple system.
Similarly, a constant pressure model is introduced in
which additional virtual volume variables are added to the
Hamiltonian. The volume and shape of the molecular dynamics
cell are now free to vary. Simple examples are discussed.
Aspects of the computer programs and the algorithms are
explained. Particular attention is focused on the methods
used to integrate the equations of motion and to calculate
the coulomb interactions.
Examples of simulations using a zirconium oxide crystal
are presented. We study the effects of heat bath and
pressure bath simulations, both separately and in
combination. Various features of the behavior are
investigated with the primary focus on phase changes,
numerical errors, and parameters describing the heat and
pressure baths. === Graduation date: 1996
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