Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 317

Important thermodynamic properties can be calculated once numerical simulations have yielded atomic configurations and velocities. The pressure is, for example, calculated from

(24)

where the bracket indicates an equilibrium time average and N, V, T, f_ij, and r_ij are as usual the number of atoms, cell volume, temperature, and pair force and distance between atoms i and j, respectively.

The internal energy (E_int) is

(25)

and the molar heat capacity at constant volume (C_v):

(26)

Alternatively, one can derive C_v from the potential energy fluctuations through

(27)

and two other interesting properties are the thermal expansion coefficient, (α_p)

(28)

where H is enthalpy, and the thermal pressure coefficient (β_V):

(29)

After a model of atomistic simulation is validated so that it can reproduce static structure of glass, it can be applied to investigate transport and dynamical properties such as diffusion constants, viscosity, or the Van Hove correlation function (Chapter 4.6).