Abstract

<sec>Researchers’ work on computational materials is often hampered by the lack of suitable intera tomic potentials. In this paper, under the framework of Finnis-Sinclair (FS) potentials, the process of fitting, testing and correction of interatomic potential is given in detail by developing the FS potential for metal Nb. First, the relationship between the interatomic potential and the macroscopic properties of the material is established. Then, the Finnis-Sinclair potential of metal Nb is fitted by reproducing the experimental data, such as the cohesive energy, bulk modulus, surface energy, vacancy formation energy and equilibrium lattice constant, and the fitting mean square error is less than 10<sup>–7</sup>. In order to test the interatomic potential, the elastic constant, shear modulus and Cauchy pressure of metal Nb are calculated by the constructed interatomic potential. In addition, how the form of the interatomic potential function affects the interstitial performance is discussed, and the constructed interatomic potential is modified according to the results of density functional theory (DFT) of the interstitial formation energy. The treatment of cutoff distance is also discussed. In the paper, the results are as follows. 1) The original form of FS potential is not suitable for extending the atomic interaction to the third nearest neighbor. Through analysis and test, it is found that when the modified electron density function is in the form of the fourth power and the form of the pair potential function is in the form of the sixth power polynomial, the interatomic potential can better describe the interatomic interaction; 2) The result of interstitial formation energy is taken as the target value to modify the behavior of the pair potential function in the near distance, and the modified interatomic potential gives the interstitial formation energy close to the result of DFT. When the interstitial energy calculated by the interatomic potential is larger than the target value, the pair potential curve of near distance will be softened by the superposition of a polynomial term, otherwise, the pair potential curve will be stiffened; 3) When the physical quantity under equilibrium state is used as the fitting data, the fitted potential parameters and the elastic constant results will not be affected, while adjusting the curve form of the potential function, as long as none of the function value, the slope and the curvature of the function curve is changed at each neighbor position. The magnitude of interstitial energy will be affected by changing the shape of the curve that is less than the first neighbor range; 4) Under the cutoff strategy in this paper, changing the cutoff distance has almost no influence on the calculated results of potential parameters or crystal properties, but has a slight influence on the mean square error of the fitting results. </sec><sec>The results of this paper provide some information for the construction of interatomic potentials database, and lay a foundation for constructing the Nb-related interatomic potential of alloy. And it also provides a method and basis for developing and improving the quality of interatomic potential.</sec>

Highlights

  • Researchers' work on computational materials is often hampered by the lack of suitable intera tomic potentials

  • the process of fitting, testing and correction of interatomic potential is given in detail by developing the FS potential

  • the Finnis-Sinclair potential of metal Nb is fitted by reproducing the experimental data

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Summary

Introduction

BeC分子基态和低激发态光谱性质和解析势能函数 Spectroscopic properties and analytical potential energy function of ground and low-lying excited states of BeC moleule 物理学报. 首先 建立原子间势与材料宏观性能之间的关系, 然后通过再现金属 Nb 的结合能、体模量、表面能、空位形成能及 平衡点阵常数的实验数据的方法拟合金属 Nb 的 Finnis-Sinclair 势. 在金属及合金中应用广泛的原子间势模型主 要是 1983—1984 年间由 Daw 和 Baskes[16,17] 提出 的 Embedded-atom method (EAM) 势模型, 以及 1984 年 由 Finnis 和 Sinclair[2] 提 出 的 FinnisSinclair (FS) 势. 1984 年 Finnis 和 Sinclair[2] 开发了 7 种 bcc 结 构金属 Nb, V, Ta, Cr, Mo, W 及 Fe 的 FS 势, 首 次考虑了原子之间的多体效应, 克服了对势的缺 点.

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