Simulation of mineral solid solutions at zero and high pressure using lattice statics, lattice dynamics and Monte Carlo methods
Simulation of mineral solid solutions at zero and high pressure using lattice statics, lattice dynamics and Monte Carlo methods
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使用晶格静力学、晶格动力学和蒙特卡罗方法模拟零压和高压下的矿物固溶体
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发表时间：
2004
期刊：
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通讯作者：
J. Purton
中科院分区：
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作者：
I T Todorov;N. Allan;M. Lavrentiev;C L Freeman;C. Mohn;J. Purton
我们讨论了两种技术，（1）晶格静态/晶格动力学模拟和（2）Monte Carlo方法的基础上，可用于计算在零和高压下的氧化物混合物的热力学性质。晶格静力学/晶格动力学计算涉及一个完整的自由能结构优化的每个配置的数量，其次是热力学平均。策略生成一组合适的配置进行了讨论。我们比较随机生成与使用径向分布函数或显式对称参数获得的结果，以获得近似或精确的权重分别为个别配置。蒙特卡罗模拟包括明确的交换阳离子和使用半随机正则系综的化学势差。这两种方法都很容易适用于高压和高温，而不需要任何新的参数化。两种方法之间的一致性在高压下更好，其中非调和项较小。我们详细比较了每种技术在零压和高压下混合的焓、熵、体积和自由能等性质的使用，从而计算了相图。我们评估这些数量的振动贡献，并与那些在稀释极限的结果进行比较。整个说明使用MnO的技术？MgO，并应易于适用于更复杂的系统。
We discuss how two techniques, based on (1) lattice statics/lattice dynamics simulations and (2) Monte Carlo methods may be used to calculate the thermodynamic properties of oxide mixtures at zero and high pressure. The lattice statics/lattice dynamics calculations involve a full free energy structural optimization of each of a number of configurations, followed by thermodynamic averaging. Strategies for generating a suitable set of configurations are discussed. We compare results obtained by random generation with those obtained using radial distribution functions or explicit symmetry arguments to obtain approximate or exact weightings respectively for individual configurations. The Monte Carlo simulations include the explicit interchange of cations and use the semigrand canonical ensemble for chemical potential differences. Both methods are readily applied to high pressures and elevated temperatures without the need for any new parametrization. Agreement between the two techniques is better at high pressures where anharmonic terms are smaller. We compare in detail the use of each technique for properties such as enthalpies, entropies, volume and free energies of mixing at zero and high pressure and thus calculation of the phase diagram. We assess the vibrational contributions to these quantities and compare results with those in the dilute limit. The techniques are illustrated throughout using MnO?MgO and should be readily applicable to more complicated systems.