Computational study of configurational and vibrational contributions to the thermodynamics of substitutional alloys: The case ofNi3Al
Computational study of configurational and vibrational contributions to the thermodynamics of substitutional alloys: The case ofNi3Al
复制标题
替代合金热力学的构型和振动贡献的计算研究：Ni3Al 的情况
DOI：
10.1103/physrevb.81.094204
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发表时间：
2009
影响因子：
3.7
通讯作者：
A. Antonelli
中科院分区：
文献类型：
--
作者：
M. Michelon;A. Antonelli
我们开发了一种方法来研究 $n$ 组分替代合金中有序-无序转变的热力学，该方法结合了非平衡方法（可以有效计算自由能）和蒙特卡罗模拟（其中在平等基础上同时考虑构型自由度和振动自由度）。此外，通过这种方法，人们可以轻松地在规范和等压等温系综中进行模拟，从而可以研究体积效应。我们应用这种方法来计算${\text{Ni}}_{3}\text{Al}$合金的熵的构型和振动贡献作为温度的函数。模拟结果表明，当系统体积保持恒定时，振动熵在转变时不会发生变化，而恒压计算表明，有序-无序转变时体积的增加导致振动熵增加$0.08{k}_{B}/\text{atom}$。与 $0.27{k}_{B}/\text{atom}$ 的构型熵增加相比，这是显着的。我们的计算还表明，仅考虑构型自由度确定的有序-无序转变温度，包含振动可降低约 30%。
We have developed a methodology to study the thermodynamics of order-disorder transformations in $n$-component substitutional alloys that combines nonequilibrium methods, which can efficiently compute free energies, with Monte Carlo simulations, in which configurational and vibrational degrees of freedom are simultaneously considered on an equal footing basis. Furthermore, with this methodology one can easily perform simulations in the canonical and in the isobaric-isothermal ensembles, which allow the investigation of the bulk volume effect. We have applied this methodology to calculate configurational and vibrational contributions to the entropy of the ${\text{Ni}}_{3}\text{Al}$ alloy as functions of temperature. The simulations show that when the volume of the system is kept constant, the vibrational entropy does not change upon transition while constant-pressure calculations indicate that the volume increase at the order-disorder transition causes a vibrational entropy increase of $0.08{k}_{B}/\text{atom}$. This is significant when compared to the configurational entropy increase of $0.27{k}_{B}/\text{atom}$. Our calculations also indicate that the inclusion of vibrations reduces in about 30% the order-disorder transition temperature determined solely considering the configurational degrees of freedom.