Modeling of configurational transitions in atomic systems

Abstract

Configurational transitions in atomic systems, i.e. transitions that change the system's geometric structure, include chemical reactions in gases, transitions between aggregate states of a polyatomic system, (the phase transitions), and nanocatalytic processes. These transitions are analyzed from the standpoint of the behavior of the system on its effective Potential Energy Surface (PES), so that the transition results from passage between different local minima of the PES. It is shown that the density functional theory (DFT) is suitable in principle for the analysis of complex atomic systems, but based on contemporary computer codes, this method cannot be used even for simple atomic systems, such as heavy atoms or metal clusters. Next, a statistical determination of energetic parameters of atomic systems does not allow to analyze the dynamics of configuration transitions; in particular, the activation energy of a chemical process differs significantly from the height of a barrier which separates the atomic configurations of the initial and final states of the transition. In particular, the statistical models, including DFT, give a melting point for clusters with a pairwise atomic interaction that is twice that from dynamic models which account for thermal motion of atoms. Hence the optimal description of configurational transitions for atomic systems may be based on joining the DFT methods for determination the PES of this system with molecular dynamics, to account for thermal motion of atoms.

Stability and Electronic Properties of PtPd Nanoparticles via MD and DFT Calculations

“…Simulation of PtPd NPs annealing was performed by MD modeling using a large-scale atomic/molecular massively parallel simulator (LAMMPS) . The MD method is widely used for investigation of structural phase transitions in metals and alloys because it allows computing dynamical characteristics of the simulated system. − According to the literature, thermodynamic properties and interaction between atoms in metallic NPs can be successfully described by various many-body potentials, namely, Sutton–Chen, Cleri–Rosato, and embedded atom method (EAM) model. − EAM potential proposed by Zhou et al was chosen to determine the interaction energy of platinum and palladium atoms, as it proved its ability to describe Pt–Pd NPs. , …”

Комплексный Статистико-Вариационный Расчет Термодинамических И Структурных Характеристик Гетерогенной Системы «кристаллическая Наночастица – Однородная Газовая Среда»

“…Введение. В данной работе анализируются разные методы теоретического описания структуры и термодинамических характеристик неоднородных молекулярных систем, в частности малых капель [1,2], что необходимо для развития теории нуклеации и кристаллических наночастиц, актуальность изучения которых обусловлена тем обстоятельством, что в настоящее время интенсивно разрабатываются экспериментальные способы получения композиционных наноматериалов, обладающих уникальными свойствами [3]. Для их описания используется метод термодинамических функционалов плотности совместно с методами коррелятивных функций в различных приближениях.…”