The Calculations Research Of The Thermodynamic Properties Of Iron Selenide And Iron Telluride

The elastic constants are very important physical quantities to crystal materials. They provide an accurate theoretical estimate for other mechanical properties of materials. The other elastic properties of materials, such as bulk modulus, shear modulus, Young's modulus and Poisson ratio, are important to the mechanical properties. It is important for the study of the mechanical properties of the materials, such as metal, fiber optic, semiconductor and so on. The thermodynamic properties are the basis of solid science and industrial applications and their study is important to extend our knowledge on their specific behavior when they undergo severe constraints of high-pressure and high temperature environments. The elastic constant and thermodynamic properties of tetragonal FeSe and FeTe were studied based on the present situation and the background were analyzed.Firstly, using the full potential linear augmented plane wave (FPLAPW) and the generalized gradient approximation (GGA) based on the density functional theory, with the theory of elasticity, the elastic constants and elastic moduli of tetragonal FeSe and FeTe at T=0 and P=0 are analyzed and predicted.Secondly, using the quasi-harmonic Debye model in which the phononic effects are considered and the GIBBS software, from the calculated E-V data at T=0 and P=0, the dependences of the volume, the bulk modulus, the thermal expansion, the Debye temperature and the heat capacity for FeSe and FeTe are obtained and the results were discussed. We find that the bulk modulus and the Debye temperatures increase with increasing pressure and decrease with increasing temperature. The heat capacity and the thermal expansion coefficient decrease with increasing pressure and increase to a constant with increasing temperature.