Calculations of the High Pressure Phase Transition Point of NaCl, KCl and NaF Crystals
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摘要: 通过晶格动力学方法，计算了NaCl、KCl和NaF晶体的NaCl（BⅠ相）结构和CsCl（BⅡ相）结构的Gibbs函数，以及晶体的BⅠ相- BⅡ相变点。计算结果表明，次近邻离子对间存在较强的短程吸引作用，对上述晶体的高压结构相变起关键作用。利用刚离子模型算得的离子势，得到了较为满意的相变点。结果还表明，温度变化对相变点的影响很小。还从Gordon-Kim模型出发，对短程作用势的物理实质作了讨论。Abstract: By using the theory of lattice dynamics, the Gibbs free energies of NaCl, KCl and NaF crystals were calculated for both NaCl and CsCl structures. Results show that the large, attractive short-range interaction between the second neigbour ions may play an important role in the explanation of the relative stability of NaCl and CsCl structures. By using the potentials obtained from Gordon-Kim model, the pressure of phase transition and the lattice constants were calculated. Results are satisfactory. The effect of temperature on the phase transition point is also investigated. The result shows that the shift in the transition point is very small when temperature changes.
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Key words:
- phase transition /
- interionic potential /
- high pressure
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