Cooling-rate dependence of thermal conductivity in a sodium silicate glass: A molecular dynamics study

Abstract

In glasses, the cooling-rate dependence of thermal conductivity has not been sufficiently studied and has not been microscopically interpreted. In this study, we investigate the cooling-rate dependence of thermal conductivity in 33.3Na₂O–66.7SiO₂ (mol.%) glasses with molecular dynamics (MD) simulations. We simulated the glasses by changing the cooling rate in the range of 0.01 to 10 K/ps, and then we calculated thermal conductivity using non-equilibrium MD. The calculated thermal conductivity was approximately 1.58 W/mK, which shows good agreement with the experimental value (1.02 W/mK). When the cooling rate was decreased, the thermal conductivity monotonically increased. To investigate the correlation between the thermal conductivity and the change in the glass structure, we defined the degree of relaxation using the Qⁿ distribution and checked the correlation. Consequently, a clear positive correlation with a correlation coefficient of 0.492 is obtained, suggesting that the dependence of the thermal conductivity on the cooling rate is attributable to the rearrangement of the medium-range structure.