Thermal and elastic properties of binary and ternary high borate glass networks from first-principles methods

Abstract The elastic properties and thermal expansion coefficients of binary and ternary high borate glass networks were studied from first principles. The calculated ground state properties (e.g., lattice constant and elastic modulus) were compared to experimental and theoretical data in the literature. The thermodynamic properties of newly discovered Rb-borates xB2O3 – yRb2O (where x = 70 or 50 mol%; y = 30 or 50 mol%), and ternary, high borate glass networks 70B2O3 - (30-x)Rb2O - xSrO (where x = 10 mol%) were evaluated through the use of quasi-harmonic approximation. It was found that with increases in boron content, the elastic moduli decrease, while the presence of Sr in Rb-borate networks, leads to a sudden increase of the moduli, closely following rules of mixtures. Thermal expansion coefficients for the studied systems are in the range of experimentally known Rb-borates - (-27) up to (+89) x 10−6 K−1.