Thermal Energy and the Equation of State for Alkali Halide Crystals

The cohesive energies and equations of state describing the pressure-volume relations are studied for nine systems of mixed alkali halide crystals for the entire range of composition. The Harrison analytical potential form for the overlap repulsive energy derived from quantum mechanical considerations is used to describe the nearest neighbour as well as next neighbour interactions. The long-range electrostatic and the short-range van der Waals interactions are also considered in the potential model. The thermoelastic properties such as the Griineisen parameter and its volume derivative, isothermal and isentropic Anderson parameters are also calculated and reported. The results are discussed and compared with experimental data.Die Kohasionsenergien und Zustandsgleichungen, die die Druck-Volumen-Beziehungen beschreiben, werden fur neun Alkalihalogenid-Mischkristallsysteme im gesamten Zusammensetzungsbereich untersucht. Die analytische Harrison-Potentialform fur die aus quantenmechanischen Betrachtungen abgeleitete repulsive Uberlappungsenergie wird benutzt, um sowohl die Wechselwirkungen nachster, als auch iibernachster Nachbarn zu beschreiben. Die weitreichenden elektrostatischen und die nahwirkenden van der Waals-Wechselwirkungen werden im Potentialmodell ebenfalls beriicksichtigt. Die thermoelastischen Eigenschaften, wie Griineisenparameter und seine Volumenableitung, isothermische und isentropische Andersonparameter werden ebenfalls berechnet und angegeben. Die Ergebnisse werden diskutiert und mit experimentellen Werten verglichen.

Cohesive Energies, Equation of State, and Thermoelastic Properties of Mixed Alkali Halide Crystals

Dixit

Niwas

1990

Equation of State and Thermal Expansivity under the Effect of High Pressure and High Temperature

Kumar

Upadhyay

1994

A simple method is developed to investigate interatomic separations and thermal expansion coefficients at pressures ranging from the atomspheric one up to the structural transition pressure, and temperatures ranging from RT to the melting temperature. The calculations are performed using an ionic model based on Harrison's quantum mechanical form for the overlap repulsive energy which takes into account the interactions up to second neighbours. The van der Waals dipole-dipole and dipolequadrupole interactions evaluated from more accurate methods are also included in the model. The results depend sensitively on temperature and pressure. The thermal expansion coefficient increases with temperature, while this increase becomes rather slow as pressure is increased. A strong decline of the thermal expansion coefficient with pressure at a constant temperature is also obtained. The results are compared with available experimental data, and good agreement supports the validity of the method developed in the present work.

Equations of State and Pressure Dependence of Bulk Modulus for NaCl Crystals

Thomas¹,

Shanker²

1995

Self Cite

Various equations of state reported in the literature are used to investigate the variation of the bulk modulus for NaCl crystals under the effect of pressure up to 300 x lo8 Pa. The results are compared with the corresponding values obtained in the present study using interionic potentials as well as with the available experimental data. Values of bulk modulus as a function of pressure are also calculated by taking into account the variation of the Anderson parameter with pressure. The results thus obtained are found to present best agreement with those estimated from the universal equation of state.