Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada.
J Chem Phys. 2011 Jan 21;134(3):034515. doi: 10.1063/1.3521485.
We analyze the C(p)-T data for the glassy state of eight materials of varied molecular interactions and structures to investigate how the use of the C(p)d ln T integral in the time-dependent (nonreversible) thermodynamic path between a liquid and glass affects our estimates of the entropy. Since the change in entropy on such a path cannot be determined, we estimate the upper and lower values of the change, Δσ, from the C(p)d ln T integral. For the same rates of cooling and heating and without annealing, Δσ on the cooling path is negligibly different from that on the heating path. The difference is ∼1∕60th-1∕25th of the lowest known value of the residual entropy and even less than the configurational entropy of the supercooled liquid at its kinetic freezing temperature. Thus use of the C(p)d ln T integral in the nonreversible path does not introduce significant errors in estimating the residual entropy. Dynamic C(p) data cannot be used to infer that configurational entropy decreases on glass formation. Time dependence of the C(p)-T path has little consequence for reality of the residual entropy.
我们分析了八种具有不同分子相互作用和结构的玻璃态材料的 C(p)-T 数据，以研究在液体和玻璃之间的时变（不可逆）热力学路径中使用 C(p)d ln T 积分如何影响我们对熵的估计。由于这样的路径上熵的变化无法确定，我们从 C(p)d ln T 积分估计熵变化的上限和下限，Δσ。对于相同的冷却和加热速率且没有退火，冷却路径上的 Δσ 与加热路径上的几乎没有区别。这种差异约为已知最小剩余熵的 1/60 到 1/25，甚至小于动力学冻结温度下过冷液体的构象熵。因此，在不可逆路径中使用 C(p)d ln T 积分不会在估计剩余熵时引入显著误差。动态 C(p)数据不能用于推断在玻璃形成过程中构象熵减小。C(p)-T 路径的时间依赖性对剩余熵的真实性几乎没有影响。
