Study Of Anharmonic Properties And Melting Law For Solids

The anharmonic properties have an important practical value. It can give the material mechanics and calorifics properties of substance system under high temperature and high pressure. Melting of solids at high temperature is a commonly observed phenomenon in nature. There have been continuing efforts to investigate the theory of melting. This paper makes a systematic study of anharmonic properties and melting law for solids at high temperatures-high pressures by using phenomenological method. Preface introduces briefly the origins and purposes of this work, the history of study of anharmonic properties and melting law and its applied subject scopes. The methods and measures used in the paper as well as its theoretical meanings and practical values have been included in preface. The first chapter systematically introduces the basic knowledge of thermodynamics properties for solids from three points of view, i.e., (1) the concept and the basic properties of solids, (2) the basic theory of thermodynamics, (3) the interaction potential among particles. Chapter two gives the new calculated formulas of Grüneisen parameter based on the second Grüneisen parameter q suggested by Jeanloz and Anderson. According to the relation between the Debye temperature and Grüneisen parameter, we can get the new calculated formulas of Debye temperature. Combine the computing model for the volume dependence of the isothermal bulk modulus BT derived by Cui and Chen, we can further get the new calculated formulas of thermal expansivity. These three new expressions have been used in NaCl, Li, Na, K and ε-Fe. The calculated results show that the agreement with the experimental data is good. In addition, we combine the He-Yan formula with the Tallon model and give the new expression of elastic constant at different temperature. The new expressions have been used to calculate second elastic constant of NaCl, KCl, CaF2, MgO, CaO and Mg2SiO4. It is found that the new method yield satisfactory results in agreement with the available experimental data. Based on the Bosi's diffusional force theory and the previous work presented by Sharma, Fang and Singh, Chapter three use more accurate formulations of potential and interionic separation and develop a suit of improved melting theory for studying the melting temperature of solids. The calculated values of Tm for a wide range of IA-VII (alkali halides), IIA-VI (alkaline-earth chalcogenides) and IA-VI (alkali chalcogenides) compounds are found to show fairly good agreement with experimental values of melting temperatures. In brief, this paper makes worthy explorations on the anharmonic properties and melting law of solids, presents some new approaches for theoretical predictions of behaviors for solids at high temperatures-high pressures. Certainly, the applications of phenomenological method may damage strictness and meticlosty of entire theories, because we must fit the experimental data to obtain some parameters and sometimes use some approximation. The tag discloses this point and several subjects that are worth, we considering, continuing to be investigated on the anharmonic properties and melting law of solids.