派热克斯玻璃的固态相变区物态方程

派热克斯玻璃的Hugoniot实验数据显示了在20GPa以下存在相变,我们认为这是一种固态-固态的一级相变,根据Gibbs相平衡条件并应用了相变前的低压物态方程,计算了这种固态-固态相变的熵增。计算表明熵增为负值,即相变为放热过程。在此基础上给出了相变区的物态方程,其中冷压为平台,内能计入了相变熵的影响。由相变区的物态方程得到的理论的与实验的Hugoniot曲线基本一致。

EQUATION OF STATE FOR PYREX GLASS IN THE REGION OF SOLID -SOLID PHASE TRANSITION

The experimental Hugoniot data obtained by Mcqueen et al1]. show that there is a plateau on D -U plane. We think this is a first order phase transition from one solid to another solid which results in a more closely packed structure and decreased compressibility. The entropy change is calculated on the basis of Gibbs equlibrium conditions, using the equation of state for low pressures. The entropy change is negative, which means that this phase transition is a exothermic process. Then the equation of state for phase transition region is achieved, where the cold pressure is constant and the energy includes the effect of the phase transition entropy. The calculated Hugoniot using the above equation of state is in agreement with experimental Hugoniot presented by Mcqueen et al.