| In a narrow sense of the word, equation of state (EOS) is the relationship of pressure, volume (or density) and temperature ( P-V-T ) for substance system in thermodynamic equilibrium. The study on the equation of state is a fundamental problem and an important content in physics. Because of the extensive applications of condensed matter in various fields, the investigations on the equation of state of compressed solids are not only necessary in many basic sciences and interdisciplinary areas, e.g. geophysics, planetary science, astrophysics, physics of condensed matter, atomic and molecular physics, thermodynamics, statistical physics, material science etc., but also of important utilized values in the explosive mechanics, energy engineering, aviation technicality and so on applied sciences.In this paper, we principally expound the fundamental theory of equation of state, theoretical models on equation of state of solids, basis of approximation, and applicable semi-empirical, semi-theoretical equation of state of solids. Following this, a new phenomenological EOS along isotherms that may be used at high pressures for NaCl-type and CsCl-type alkali halides, metals, periclase (MgO), rare-gas Xenon solid, and so on, is presented, by making use of the definition of short-distance repulsive force constant (A) and the phenomenological function A(r). In addition, a newphenomenological EOS is proposed along isobars that may be applied at high temperatures and high pressures for 16 alkali halide crystals, 6 minerals, and so on, by taking advantage of the hypothesis that Anderson-Griineisen parameter 5T is the function of volume (V) along isobars. And the validity and application of the EOSs presented in this paper are studied and discussed.In the introduction, we briefly describe the fundamental conceptions of equation of state, overview its development history, illustrate its typical applications in many fields, and recommend its predominant methods of investigating EOS at present.In the second chapter, the conceptions of solids-------structure, compressibility,expansivity, specific heat capacity, bulk modulus, and some nonlinear parameters are reviewed and elaborated. The basic theory in the broad sense and polynomial forms of EOSs are stated. The emphasis in this chapter is to state the principles of energy and pressure of crystals in static situation (when temperature 7= OK), the Mie-Griineisen relationship, describing the vibrational energy (thermal energy) and thermal pressure (Plh) of crystals, and Debye model and Debye equation of state for "ideal" solids.In chapter three, the present equations of state (EOSs) used constantly by many investigators are classified and elucidated by virtue of theory foundations, phenomenological potential models, experimental bases, and the applied conditions of EOSs. In view of the applied condition, the equations of state are assorted as follows: isothermal EOS, isobaric EOS, and high-temperature EOS. The examinations on the applicability and validity of the equations of state along isotherms and along isobars are made for alkali halides, alkali oxides, and some minerals. The theoretical calculated data of (P-F/F0), (BT-VIV0), (V/V0-T), (r-T), (BT-T) and (a.-T) are compared with each other as well as the available experimental data. The results demonstrate that the theory predicted values of compression, bulk modulus, linear expansion, and thermal expansive coefficient of compressed solids are very agreement with the corresponding experimental data. In summary, the error with respect to theory prediction and its causes are probably analyzed in detail. The discussion suggests that the function of the phenomenological short-distance repulsive force constant A(V) and approximation for Anderson-Griineisen parameter 5T(V) proposed in this paper are valid and applicable in high pressures (up to lOOGPa) and high temperatures (from Debye temperature 0D to melting temperature Tm) for many types of solids. |
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