Коллективные движения атомов в кристаллах

Математическое моделирование. 2023. Т. 35. № 6. С. 37–50.

Norman G., Fleita D., Негодин В. Д.

The collective motions of atoms in the molecular dynamics model of a classical Lennard- Jones
monocrystal are studied in the process of heating up to a spinodal decomposition and subsequent
cooling of the melt until spontaneous crystallization. A hysteresis in the degree of collectivity of
atomic motions is found. A new numerical method based on the use of a four-point correlator is used
to study the collectivity in the motion of atoms in crystals. This correlator represents the mean cosine
of the angle between the displacement vectors of two atoms over time, which were initially close to
each other. Two features are found: (a) the correlator increases with the temperature in the monocrys-
tal; (b) the correlator in the polycrystal, which was formed during crystallization, appears to be higher
than in the initial monocrystal. The distributions of the correlator’s values over the angles between dis-
placements are computed. Two contributions to the atoms’ motions are distinguished: an anisotropic
motion, which does not depend on temperature, and an almost isotropic motion, whose angular dis-
tribution has the form of a Boltzmann distribution. The excitation energies, which corresponds to the
second contribution, are calculated.

Keywords: корреляционные функции, correlation function, классическая молекулярная динамика, classical molecular dynamics