CALCULATION OF MELTING CURVES AND PARAMETERS OF SHOCK COMPRESSION OF METHANE CHLORINE DERIVATIVES

V.V. Dryomov, D.G. Modestov
VANT. Ser.: Mat. Mod. Fiz. Proc 1997. Вып.1. С. 48.

      Model equation of state for methane chlorine derivatives is constructed on the basis of variation theory of perturbations [1]. Directly for the calculations we use proposed by Ross decomposition of free energy with base potential of solid spheres and with correction for agreement with results of computer modeling of a system of particles interacting through potential R-12 [2]. To describe interaction between molecules potential exp-6 was used in this work [3] which describes this class of substances well. To calculate melting curves analog of Lindeman’s law of melting is used, namely, constancy of package parameter along the melting curve ( for liquid we must speak about solidification curve) [4].
      This work provides comparison with experimental data on melting of methane chlorine derivatives under low pressures. It is shown that dichloromethane and chloroform are liquids under shock compression. As to carbon tetrachloride, even under low pressures it transforms into solid state and melts only under pressures on the order of 25-30 GPa.
      To describe experimental data on shock compression [5] under high pressures where Hugoniots of methane chlorine derivatives have a break, dissociation was introduced into the model. To describe
      a multi-component mixture we used one-liquid Van der Waals’s model (see, e.g., [3]). It is
      shown that in the region of experimental Hugoniots breaks a considerable role is played by disbalance. Comparison with experimental values of shock front temperature [6] besides that shows influence of oscillatory relaxation upon measurement results under low temperatures. Comparison is also given for calculated and experimental sound velocity [6] behind the shock front.
      1. Barker J.A., Henderson G. // Rev. Mod. Phys. 1976. Vol. 48. P. 587.
      2. Ross M. // J. Chem. Phys. 1979. Vol. 71. P. 1567.
      3. Ree F.N. // J. Chem. Phys. 1984. Vol. 81, N 3. P. 1251.
      4. Ross M.//Phys. Rev. 1973. Vol.-8, N 3. P. 1466.
      5. Dick R.D. // J. Chem. Phys. 1981. Vol. 74, N 7. P. 4053.
      6. Gogulya M.F., Dolgoborodov A.Yu. // Chemical Physics. 1994. Vol. 13, N 12. P. 118.