Zr在αU中的固溶度曲线的第一性原理计算

First principles calculations of the solid solubility curve of Zr in αU

摘要:

针对U-Zr相图中富U端Zr在αU中的固溶度曲线所需的溶解焓和过剩熵，本文分别进行了第一性原理计算并与实验数据进行了对比分析。对于Zr-αU固溶体转变为δUZr2时对应的溶解焓和过剩熵，采用SQS模型得到每个Zr原子对应的结果为1.437 eV/Zr和1.060 kB/Zr，采用disorder模型得到每个Zr原子对应的结果为1.420 eV/Zr和 0.732 kB/Zr。基于实验数据，分析拟合得到的每个Zr原子的溶解焓为-0.823±0.712 meV/Zr，过剩熵为5.880±9.976 kB/Zr。对比理论计算和拟合实验数据的结果发现，振动熵对固溶度的影响不可忽略，并且理论和实验数据相差较大的原因可能与理论计算中设置的δUZr2中Zr的位置与实验中的具体结构位置参数不尽相同有关。

Abstract:

The solution enthalpy and the excess entropy of Zr in αU have been calculated based on first principles calculations in order to achieve U-rich solubility curves for U-Zr phase diagram. The enthalpy and the excess entropy of the Zr atom corresponding to Zr-αU transforming from solution state into δUZr2 are 1.437 eV/Zr atom and 1.060 kB/Zr atom by using the SQS model, which are 1.420 eV/Zr atom and 0. 732 kB/Zr atom with the disorder structure for δUZr2. But based on the experimental data, the fitted solution enthalpy and excess entropy are -0.823±0.712 meV/Zr atom and 5.880±9.976 kB/Zr atom, respectively. Through comparing the theoretical calculations and the experimental fitting results, it is found that the effect of the vibrational entropy on solubility could not be ignored. This discrepancy between the theoretical results and the experimental data might be related to the fact that the positions of Zr in δUZr2 in the theoretical calculations are not well consistent with the specific structural parameters of the the experimental samples.