Origin Of The T1+Alpha Dependence Of The Heat Capacity Of Glasses At Low Temperature

We address the issue of the experimentally observed deviation of the heat capacity of glasses from linearity at low temperatures Tsimilar to1 K. The energy spectrum of an anharmonic oscillator in a double-well potential is calculated, using parameters from recent molecular dynamics simulations of two-level systems in silica glass. A model that accounts for the contribution of more than two lowest.-energy levels of a single anharmonic oscillator to the heat capacity at Tsimilar to1 K is proposed and is shown to describe the experimentally observed proportional toT(1.3) behavior of the heat capacity of silica glass.