Temperature dependence of elastic constants and thermal expansion coefficient for NaCl crystals

Abstract

The second-order elastic constants (711, (712, and C 4 4 , isothcrmal bulk modulus BT, and volume thermal expansion coefficient a are calculated for NaCl crystals in the temperature range (294 to 766 K) using Tallon's model based on the concept of modified Anderson-Griineisen parameters. The results obtained in the present study arc compared with the experimental values reported in the literature. There is good agreement between calculated and experimental values for V/Vo, C11, Cd4, BT, and a. It is found that C11, (244, arid BT decrease whereas C 1 2 and a increase with increase in temperature.

Relation between thermal expansivity and bulk modulus for ionic solids at high temperatures

“…In these studies, thermal expansivity has been examined in the range between room temperature and melting temperatures with different approximations and best-fit relations. These attempts [6][7][8][9][10][11] have not been very successful and there is an urgent need for developing a simple method which can yield reliable values of thermal expansivity along with the values of isothermal bulk modulus for solids at high temperature conditions. In the present study we have used the thermodynamic data reported by Anderson [1] and the data extrapolated by Singh and Chauhan [12] to establish a new relationship between thermal expansivity and isothermal bulk modulus for NaCl, KCl, MgO and CaO corresponding to a wide range of temperatures.…”

“…It is, therefore, desirable to develop semi-empirical or semi-phenomenological models for predicting a in those regions where no experimental data are available, in addition to theoretical abinitio calculations, which often give approximate or qualitative results at high temperatures [4,5]. Various attempts [6][7][8][9][10][11] have been made for investigating the temperature dependence of thermal expansivity by considering its linear as well as nonlinear dependences. In these studies, thermal expansivity has been examined in the range between room temperature and melting temperatures with different approximations and best-fit relations.…”

Temperature dependence of interatomic separation for alkali halides

“…In addition, I would like to point out an interesting fact that the Tallon's model [24], as is believed [25,26] to be very suitable for the elastic behavior of solids in a wide range of temperature, can be yielded simply from this work. This may be described as below.…”

Thermophysical properties of rubidium and lithium halides by γ-ray attenuation technique

“…For LiCl the temperature dependence of density is represented by linear equation ρ(T) = (2131 ± 9.66) + (-3.27 × 10 ± 1.78 × 10 )T. (19) The coefficient of temperature dependence of den sity is -0.327 kg m -3 K -1 and the coefficient of volume thermal expansion is 1.58 × 10 -4 K -1 in the tempera ture range 300-750 K. The thermal expansion increases linearly with temperature and the results on thermal expansion is represented by the linear equa tion Δl/l = (-10.40 ± 0.56) + (7.44 × 10 ± 1.03 × 10 )ΔT. (20) Rapp and Merchant [32] have studied the thermal expansion of LiCl from 70 to 570 K using dilatometer method. The results obtained in the present work for LiCl have been shown in Fig.…”

“…The density and thermal expansion of solids at high temperature can be determined by number of methods like Archimedean method, pycnometry, dilatometry, and electromagnetic levitation, Method of maximal pressure in gas bubble, method of sessile drop, hydrostatic weighing, high temperature electro static levitation [4] and gamma ray densitometry [5][6][7][8][9]. Thermal expansion studies on alkali halides have been reported by several workers using X ray diffraction [10,11], dilatometry [12,13], Fabrey Perot interfer ence method [14] and by other theoretical models [15][16][17][18][19][20][21][22]. Such studies on alkali halides by γ ray atten uation technique are lacking.…”