STUDY ON THERMODYNAMIC PROPERTY OF THIN FILM OF BCC INTERSTITIAL ALLOY WSi AT ZERO PRESSURE: DEPENDENCE ON TEMPERATURE, INTERSTITIAL ATOM CONCENTRATION AND FILM THICKNESS

The article presents a model and derives analytical expressions for Helmholtz free energy, the nearest neighbor distance, isothermal compressibility, the thermal expansion coefficient, the heat capacities at constant volume and constant pressure as functions of temperature, concentration of interstitial atoms, and film’s thickness for an interstitial binary alloy with a BCC structure based on the statistical moment method (SMM). The theoretical results are applied to numerical calculations for films of W and WSi. The temperature and interstitial atom concentration dependences of thermodynamic quantities for the alloy WSi’s film are similar to those for the metal W film. When the film thickness increases to about 40 nm, the thermodynamic properties of the film approach those of the bulk material. The SMM numerical results for W agree well with experimental data and other calculation results. Other SMM numerical results are new and predict future experimental results.