In the following section, we present a set of case studies that illustrate the fundamental concepts dis­cussed earlier. The examples are chosen to reflect the application of MD to mechanical properties of crystalline solids and the behavior of defects in them. More detailed discussions of these topics, especially in irradiated materials, can be found in Chapter 1.11, Primary Radiation Damage For­mation and Chapter 1.12, Atomic-Level Level Dislocation Dynamics in Irradiated Metals.

1.09.6.1 Perfect Crystal

Perhaps the most widely used test case for an atomis­tic simulation program, or for a newly implemented potential model, is the calculation of equilibrium lattice constant a0, cohesive energy Ecoh, and bulk modulus B. Because this calculation can be performed using a very small number of atoms, it is also a widely used test case for first-principle simulations (see Chapter 1.08, Ab Initio Electronic Structure Cal­culations for Nuclear Materials). Once the equilib­rium lattice constants have been determined, we can obtain other elastic constants ofthe crystal in addition to the bulk modulus. Even though these calculations are not MD perse, they are important benchmarks that practitioners usually perform, before embarking on MD simulations ofsolids. This case study is discussed in Section 1.09.6.1.1.

Following the test case at zero temperature, MD simulations can be used to compute the mechanical properties of crystals at finite temperature. Before computing other properties, the equilibrium lattice constant at finite temperature usually needs to be determined first, to account for the thermal expan­sion effect. This case study is discussed in Section 1.09.6.1.2.