极端条件下铁的相互作用势

魏良睿; 孙阳

doi:10.11858/gywlxb.20251251

极端条件下铁的相互作用势

doi: 10.11858/gywlxb.20251251

魏良睿,
孙阳^*, ,

厦门大学物理科学与技术学院, 福建厦门　361005

基金项目: 国家自然科学基金（T2422016，42374108）

详细信息

作者简介:
魏良睿（2002－），男，硕士研究生，主要从事地核下富铁固溶体相图研究. E-mail：19820241154118@stu.xmu.edu.cn

通讯作者:
孙　阳（1990－），男，博士，教授，主要从事极端条件下物性与相变研究. E-mail：yangsun@xmu.edu.cn

中图分类号: O521.2
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出版历程
- 收稿日期: 2025-11-06
- 修回日期: 2025-12-22
- 网络出版日期: 2025-12-24

Interatomic Potentials for Iron under Extreme Conditions

WEI Liangrui,
SUN Yang^{*
, ,}

Department of Physics, Xiamen University, Xiamen 361005, Fujian, China

摘要

摘要: 铁在极端高温高压条件下的物理性质对于理解地球及类地行星内部结构和演化过程具有重要意义。为了刻画铁在超级地球内部极端条件下的动力学行为，结合第一性原理分子动力学模拟与实验测定的高压熔化曲线，构建了一套适用于超高压力与高温范围的嵌入式原子势函数。该势函数拟合了体心立方相、密排六方相和液相在400 GPa～1 TPa、6000～10000 K下的多项物理性质，包括固态的弹性常数、液态的径向分布函数，以及实验获得的熔化曲线。在不同温压条件下对该势函数进行了系统检验，结果表明：其能够准确再现固态弹性常数与压力及温度的依赖关系；在3组典型温压点上与液相径向分布函数一致；预测的熔化曲线处于实验误差范围内，并且与第一性原理模拟结果基本吻合。基于该势函数的热力学计算进一步表明，在400 GPa～1 TPa压力区间内，铁的密排六方相保持热力学稳定，而体心立方相呈亚稳态。该势函数为大尺度模拟超级地球核心的形核结晶与固液共存提供了可靠的原子级工具；同时，该势函数与数据集为后续扩展多组分铁合金在超高压条件下的物性研究奠定了基础。
- 铁 /
- 高温高压 /
- 嵌入原子方法 /
- 熔化曲线 /
- 分子动力学
Abstract: The physical properties of iron under extreme high-pressure and high-temperature conditions are crucial for understanding the internal structure and evolutionary processes of Earth and terrestrial planets. To characterize the dynamic behavior of iron under the extreme conditions inside super-Earths, we combine first-principles molecular dynamics simulations with experimentally measured high-pressure melting curves to construct an embedded-atom potential applicable across ultra-high pressures and temperatures. This potential is fitted to multiple properties of the body-centered cubic (BCC), hexagonal close-packed (HCP), and liquid phases over 400 GPa to 1 TPa and 6000 to 10000 K, including the elastic constants of the solid phases, the radial distribution functions of the liquid, and experimentally determined melting data. We systematically validate the potential across different pressure-temperature conditions and found that it accurately reproduces the pressure and temperature dependence of solid elastic constants, and matches liquid radial distribution functions at three representative pressure-temperature conditions. Moreover, it predicts melting curves that lie within experimental uncertainties and agree well with previous first-principles simulations. Thermodynamic calculations based on this potential further show that the HCP phase remains thermodynamically stable between 400 GPa and 1 TPa, while the BCC phase is metastable. This potential provides a reliable atomistic tool for large-scale simulations of nucleation, crystallization, and solid-liquid coexistence in the cores of super-Earths. Moreover, the potential and associated dataset lay the groundwork for future extensions to multicomponent Fe alloys and their properties under ultra-high-pressure conditions.
- iron /
- high temperature and high pressure /
- embedded atom method /
- melting curve /
- molecular dynamics

HTML全文

图 1 BCC相和HCP相的弹性常数

Figure 1. Elastic constants for BCC and HCP phases

下载: 全尺寸图片幻灯片

图 2 液相g(r)

Figure 2. Liquid radial distribution function

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图 3 铁的熔化曲线

Figure 3. Melting temperature lines of iron

下载: 全尺寸图片幻灯片

表 1 第一性原理模拟得到的BCC相和HCP相的晶格常数和平衡压强

Table 1. Lattice constants and equilibrium pressures of BCC and HCP phases from ab initio simulations

Phase	T/K	p/GPa	a/Å	Phase	T/K	p/GPa	a/Å	c/Å
BCC	6000	396	2.37	HCP	6000	350	2.15	3.42
	8500	665	2.27		8500	671	2.03	3.25
	10000	1078	2.16		10000	1000	1.95	3.14

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表 2 第一性原理模拟得到的BCC相和HCP相的弹性常数

Table 2. Elastic constants for BCC and HCP phases from ab initio simulations

Phase	T/K	p/GPa	C₁₁/GPa	C₁₂/GPa	C₁₃/GPa	C₃₃/GPa	C₄₄/GPa
BCC	6000	396	1462	1462			331
	8500	665	2146	2146			457
	10000	1078	3243	3337			667
HCP	6000	350	1571	1173	1042	4134	211
	8500	671	2639	2158	1767	2886	318
	10000	1000	3407	3151	2427	1882	488

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表 3 第一性原理模拟得到的液相密度和平衡压强

Table 3. Liquid densities and equilibrium pressures from ab initio simulations

T/K	p/GPa	Density/(g·cm⁻³)
6000	360	13.441
8500	596	15.202
10000	958	17.428

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表 4 实验^[17]得到的HCP相在不同压强下的熔点

Table 4. Melting temperatures of HCP phase at different pressures from experiment^[17]

p/GPa	$ T_{\mathrm{m}}^{\text{hcp}} $/K
360	6503
584	8342
990	11027

下载: 导出CSV

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