Hindawi Publishing Corporation Physics Research International Volume 2011, Article ID 186704, 6 pages doi:10.1155/2011/186704 Research Article Isobaric Study of the Elastic Properties for Alkaline Earth Oxides under High Temperature Seema Gupta, 1, 2 S. P. Singh, 2 and S. C. Goyal 1, 2, 3 1 Department of Physics, Agra College, Agra 282002, India 2 Department of Physics, Goverment Degree College, Sambhal, Moradabad, India 3 K. P. Engineering College, N. H. 2, Etmadpur, Agra 283202, India Correspondence should be addressed to Seema Gupta, seema g khushi@yahoo.co.in Received 20 September 2010; Revised 7 March 2011; Accepted 9 March 2011 Academic Editor: Fahrettin Yakuphanoglu Copyright © 2011 Seema Gupta et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A simple and straightforward theoretical model is developed to investigate the elastic properties of alkaline earth oxides under the effect of temperature as well as pressure. The calculation is performed with the help of high pressure-high temperature equation of state based on thermodynamic analysis. The anharmonic term arising due to thermal expansion has been taken into account in the expansion of logarithmic series of the thermodynamic data. The results obtained for alkaline earth oxides are discussed and compared with experimental data under the combined effect of high temperature and high pressure. The results are found to be in good agreement with available experimental results. 1. Introduction The equation of state (EOS) gives us valuable information about the change in bulk under the influence of temperature at a fixed pressure and is thus related to the compression of solids. The study of elasticity plays an important role in describing the high-temperature behaviour of solids. The studies based on the equation of state (EOS) are vide importance in physics as well as in chemistry and in the earth sciences [1, 2]. The theoretical studies of EOS at high temperature and pressure are of fundamental interest because they permit interpolation and extrapolation into the regions in which the experimental data are spares or lacking. It is the necessary to know the effects of the temperature and pressure on the elastic properties of alkaline earth oxides (AEOs) throughout the upper mantle of the Earth for better understanding about its structure, compositions, and mineralogy. The properties of alkaline earth oxides solids under varying conditions of temperature and pressure have attracted the attention of theoretical and experimental workers [3–9] because of their need in different branches of science [10]. The problem of evaluation of elastic moduli can be tackled in two different ways, for example, (i) by deter- mining the constants or elastic moduli from temperature relationship, termed as equation of state [3–7] and (ii) by choosing suitable interionic potential and there by evaluating elastic constants and elastic moduli [11–13]. Both methods help us to determine various properties of solids under varying conditions of pressure and temperature. It has been observed that the methods based on the theory of interionic potentials are very tedious [11–16] and involve a lot of computational work in addition to various approximation and it fails to evaluate the elastic constants or elastic moduli of complicated solids. The purpose of the present study is to present a simple and straightforward method for evaluation of elastic constants of simple and complex solids at different tem- peratures. To determine the temperature dependence of elastic constants and their combination, different relations based on thermodynamic parameters have been proposed in the literature [17]. The well-known and widely used relations for predicting the temperature dependence of elastic constants are discussed by Suzuki et al. [18] and by