Theoretical and Computer Simulation Studies on Freezing of Liquids and Surface Melting

本课题的研究目的是建立固液相变理论，并最终从微观角度研究表面熔化等表面和界面的相变。固液相变是日常生活中最常见的相变，但其研究还远远不是基于第一性原理的微观相变。近年来，密度泛函冻结理论已被公认为是研究固液转变的有力基础，并发展了许多理论。这些理论对于通过短程势相互作用的系统已经证明是成功的，但它们不能预测实际系统（特别是库仑液体）的冻结，这个问题仍然没有解决。本研究从分析这些故障的原因开始，在此基础上，提出了一种新的理论，并成功地应用于各种系统，如经典的单组分等离子体和逆功率系统。这个理论是基于热力学微扰方法的思想，可以看作是它对非均匀液体的推广。我们现在正在进行研究，以推广上述理论，使其适用于液体表面和固液界面。在上述研究的同时，我们对小颗粒进行了基础研究，以发现表面的存在和系统的有限性对电子性质的影响。我们剩下的项目是将这些研究与统计力学方法结合起来，并将其应用于表面和界面的各种现象。

The purpose of this research project is to establish theory of the solid-liquid phase transition and as the final goal to study phase transitions at surfaces and interfaces such as the surface melting from microscopic point of view. The solid-liquid transition is the most popular phase transition in daily life, but its studies have been far from microscopic one based on first principles. Recently, the density functional theory of freezing has been recognized as a powerful root to the study of the solid-liquid transition and several theories have been developed. These theories have proved successful for systems interacting through short-ranged potentials, but they fail to predict freezing of realistic systems (especially, Coulombic liquids) and this problem has been remained unsolved. The present study started with the analyzes of the reasons for these failures and, based on these analyzes, we formulated a new theory and successfully applied it to various systems such as the classical one-component plasma and the inverse-power systems. This theory is based on the idea of the thernodynamic perturbation approach and can be viewed as its generalizaiton to nonuniform liquids. We are now proceeding with the study to generalize the above theory such that it can be applicable to the liquid surfaces and solid-liquid interfaces.In parallel with the above studies, we performed a basic study on small particles to find how the electronic properties are influenced by the presence of surface and by the finiteness of system. It is our remaining project to combine these studies with the statistical-mechanical approach and to apply it to various phenomena at surfaces and interfaces.