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以面心立方金属钯为研究对象,基于第一性原理中的局域密度近似理论(LDA),计算了不同晶格长度下的原子间内聚能并得到其原子内聚能曲线。通过陈-莫比乌斯晶格反演势理论,得到了精确的反演对势曲线。采用不同势函数对该曲线拟合,通过对拟合效果的对比和分析,提出了全局精度较高的双指数型势函数。同时,分别采用第一性原理方法,原子嵌入势(EAM)方法和反演势数据计算了钯的声子谱。比较声子谱曲线发现,曲线的变化趋势是相似的,说明反演势可以合理的反应原子间相互作用。并且反演势方法所需的计算时间明显少于EAM势方法,说明反演势方法在计算量上有明显优势。最后,计算了金属钯的热膨胀系数,弹性模量和格林乃森常数等物理量。计算结果与实验数据基本符合,表明构建的钯的反演势是准确有效的。
Based on the first-principles approximation theory of local density (LDA), the interfacial cohesive energy with different lattice length was calculated and the atomic cohesive energy curve was obtained. By Chen-Mobius lattice inversion potential theory, we get the accurate inversion potential curve. The curves were fitted by different potential functions. Based on the comparison and analysis of fitting results, a double exponential potential function with high global accuracy was proposed. At the same time, the phonon spectra of palladium were calculated by the first principle method, the atomic insertion potential (EAM) method and the inversion potential data respectively. Compared with the phonon spectrum curve, the trend of the curve is similar, indicating that the inversion potential can reasonably reflect the interaction between atoms. And the computational time required by the inversion method is less than that of the EAM method, which shows that the inversion method has obvious advantages in calculation. Finally, the thermal expansion coefficient, elastic modulus, and Green’s modulus of the metal palladium are calculated. The calculation results are in good agreement with the experimental data, indicating that the built-up palladium inversion potential is accurate and effective.