Atomic diffusion is a spontaneous process and significantly influences properties of materials, such as fracture toughness, creep-fatigue properties, thermal conductivity, thermoelectric properties, etc. Here, using extensive molecular dynamics simulations based on both ab initio and machine-learning potentials, we demonstrate that an atomic one dimensional cooperative diffusion exists in the simple cubic high-pressure finite-temperature phase of calcium in the premelting regime, where some atoms diffuse cooperatively as chains or even rings, while others remain in the solid state. This intermediate regime is triggered by anharmonicity of the system at high temperature and is stabilized by the competition between the internal energy minimization and the entropy maximization, and has close connections with the unique electronic structures of simple cubic Ca as an electride with a pseudogap. This cooperative diffusion regime explains the abnormal enhancement of the melting line of Ca under high pressure and suggests that the cooperative chain melting is a much more common high-temperature feature among metals under extreme conditions than hitherto thought. The microscopic electronic investigations of these systems combining ab initio and machine-learning data point out the direction for further understanding of other metallic systems such as the glass transition, liquid metals, etc.

中文翻译：

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简单立方晶体中的电子驱动一维合作扩散

原子扩散是一个自发过程，会显着影响材料的性能，例如断裂韧性，蠕变疲劳性能，热导率，热电性能等。这里，基于从头算起使用广泛的分子动力学模拟和机器学习潜能，我们证明了在预熔化状态下钙的简单立方高压有限温度相中存在原子一维协同扩散，其中一些原子以链或环的形式协同扩散，而另一些原子则保留在环中。固体状态。该中间态由高温下的系统非谐性触发，并通过内部能量最小化和熵最大化之间的竞争而稳定，并且与简单的立方Ca的独特电子结构紧密相连，作为具有拟间隙的电子。这种协同扩散机制解释了在高压下Ca熔解线的异常增强，并表明在极端条件下金属间的协同链熔解是比以往所认为的更为普遍的高温特征。这些系统的微观电子研究相结合从头算和机器学习数据指出了进一步理解其他金属系统（如玻璃化转变，液态金属等）的方向。