High configurational entropy driven increased heat capacity of refractory multicomponent di-silicides

Abstract

The high melting point of refractory di-silicides e.g., MoSi2, WSi2, and VSi2, together with their strong resistance to creep and high temperature oxidation, have promoted their potential for use in harsh environments. To realize this promise, an enhanced heat capacity and reduced thermal expansion coefficient are critical for using di-silicides in heat shields and jet engines. Using first principles, we reveal that cationic disordered multicomponent di-silicides with tetragonal structure possess multi-fold higher heat capacity (Cp), and a reduced volumetric thermal expansion coefficient, relative to their low-entropy counterparts. An increase in configurational entropy contributes to metallic bonding, delocalized electrons and a high degree of degeneracy of the optical phonons. Additionally, the average atomic mass, gradient of the dispersion curve and acoustic softening contribute to the variations in the phonon group velocities and subsequently impact the thermal properties.