稀有元素的固液共存。I. 以氩为例阐述理论
Solid-liquid coexistence of the noble elements. I. Theory illustrated by the case of argon
AI总结：
本研究使用SAAP势函数进行分子动力学模拟，验证了氩的隐藏标度不变性，并利用同构理论准确预测了其固液相变性质，发现bcc晶体在高压下稳定。
摘要：
稀有元素构成最简单的原子组。在低温或高压下，它们冻结成面心立方（fcc）晶体结构（除氦外）。我们使用最近提出的简化从头算原子（SAAP）势[Deiters and Sadus, J. Chem. Phys. 150, 134504 (2019)]进行分子动力学模拟。该势函数通过CCSD(T)级别的耦合簇方法进行的精确从头算量子力学计算数据进行了参数化。我们计算了氩的fcc凝固线，发现与实验值高度吻合。在低压下，通过使用多体校正进一步增强了这种一致性。通过计算恒定过剩熵线（构型绝热线），验证了势能函数的隐藏标度不变性，并表明均方位移和静态结构因子是不变的。这些线（同构线）可以通过了解对势，从单一状态点的模拟中生成。固液转变的同构理论被用于准确预测压力-温度平面中凝固线的形状、密度-温度平面中的形状、熔化熵以及沿熔化线的Lindemann参数。我们最终预测体心立方（bcc）晶体在高压下是稳定的。
英文摘要：
The noble elements constitute the simplest group of atoms. At low temperatures or high pressures they freeze into the face-centered cubic (fcc) crystal structure (except helium). We perform molecular dynamics using the recently proposed simplified ab initio atomic (SAAP) potential [Deiters and Sadus, J. Chem. Phys. 150, 134504 (2019)] . This potential is parameterized using data from accurate ab initio quantum mechanical calculations by the coupled-cluster approach on the CCSD(T) level. We compute the fcc freezing lines for Argon and find a great agreement with the experimental values. At low pressures, this agreement is further enhanced by using many-body corrections. Hidden scale invariance of the potential energy function is validated by computing lines of constant excess entropy (configurational adiabats) and shows that mean square displacement and the static structure factor are invariant. These lines (isomorphs) can be generated from simulations at a single state-point by having knowledge of the pair potential. The isomorph theory for the solid-liquid transition is used to accurately predict the shape of the freezing line in the pressure-temperature plane, the shape in the density-temperature plane, the entropy of melting and the Lindemann parameters along the melting line. We finally predict that the body-centered cubic (bcc) crystal is stable at high pressures.
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