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Phase transitions and adjacent phenomena in simple atomic systems

机译：简单原子系统中的相变和相邻现象

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摘要

Clusters and bulk systems of bound atoms with pairwise interactions have two types of excitations: configurational, due to a change in the atomic arrangement in space, and thermal, associated with atomic vibrations. The configurational excitation is responsible for phase transitions in such systems and can be considered as a transition from the global minimum of the atomic potential energy surface in a multidimensional space of atomic coordinates to some other, higher-energy local minima. From this standpoint, various aspects of aggregate states of atomic clusters are considered, including coexistence of the liquid and solid cluster phases, the freezing point as the temperature of transition from the metastable liquid state to the unstable state, the glassy states as unstable configurationally excited states with long lifetimes, and the phase transition under high pressures when the crystal lattice for the distribution of atoms is no longer the most stable form for the solid state. The concept of voids as elementary internal configurational excitations of a macroscopic atomic system, which are connected with local minima of the potential energy surface, allows us to consider the glassy-solid transition and processes of the growth of nuclei of a new phase as a result of void transport. The degrees of deviation from traditional macroscopic thermodynamics for clusters and bulk systems near a phase transition is analyzed. It is shown that the thermal motion of atoms makes a significant contribution to the entropy jump at the phase transition, which allows us to use the Lindemann criterion for the phase transition and other criteria which use parameters of thermal motion of atoms, even though the inherent nature of the phase transition is determined by configurational excitation.
机译：具有成对相互作用的结合原子的团簇和本体系统具有两种类型的激发：由于原子在空间中的变化而导致的构型激发，以及与原子振动相关的热激发。构型激发负责这种系统中的相变，并且可以被认为是从在原子坐标的多维空间中的原子势能面的全局最小值到其他更高能量的局部最小值的过渡。从这个角度出发，考虑了原子团簇的聚集态的各个方面，包括液态和固态团簇相的共存，凝固点（从亚稳态液态到不稳定态的转变温度），玻璃态（不稳定的构型激发态）。当原子分布的晶格不再是固态的最稳定形式时，其寿命长，并且在高压下发生相变。空隙的概念是宏观原子系统的基本内部结构激发，与势能面的局部极小值相关，因此我们可以考虑玻璃态-固态转变和新相核的生长过程。无效的运输。分析了相变附近的团簇和本体系统与传统宏观热力学的偏离程度。结果表明，原子的热运动对相变过程中的熵跃迁做出了重要贡献，这使我们可以将林德曼准则用于相变，以及使用其他准则来利用原子的热运动参数，即使固有相变的性质由构型激发确定。

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