摘要
通过第一性原理方法系统地研究了Ag-La系四种二元化合物的相结构稳定性和电子结构,包括B2-La Ag、La Ag2、La14Ag51和α-La Ag5。结构优化后的平衡态晶体参数及质量密度与实验值相符。结合能表明,随La浓度的增加,化合物的键合强度和稳定性提高。Ag-La系4种二元化合物的生成焓分别为-21.7,-26.8,-22.9,-18.1 k J/mol,与实验值或CALPHAD的理论值相符。电子结构表明这些化合物是导体,其原子间的价键性质是由金属键、离子键和共价键构成,其中:离子键是由Ag原子从La原子中得到电子形成的,共价键是由Ag s-p及Ag p-La d杂化构成的。并且这些化合物的共价键和离子键随着La浓度的增加而增强,使得Ag-La化合物稳定性提高。
The first-principle calculation was performed to investigate the phase stability and electronic structure of four typical binary Ag-La compounds, including B2-LaAg, LaAg2, Lal4 Ag51and α-LaAg5. The optimizedstructural parameters and mass densities of equilibrium were consistent with experimental data. The calculated cohesive energies indicate that the bond strength and stability of the four compounds is gradually enhanced with increasing La concentration. And enthalpies of formation of compounds are also consistent with experiment and CALPHAD calculation values, and their values are -21.7, -26.8, -22.9 and - 18.1 kJ/mol, respectively. The results of electronic structure reveal that all Ag-La binary compounds analyzed here are conductors, and metallic, ionic and covalent bonds are involved. The ionic bond is attributed to charge moving from La atoms to Ag atoms, and the covalent bond is comprised of the hybridization of Ag s-p and Ag p-La d. With increasing La concentration in Ag-La compounds, both the strength of ionic and covalent bond are strengthened, leading the increasing of the stability of the compounds.
出处
《重庆理工大学学报（自然科学）》
CAS
2016年第8期45-51,68,共8页
Journal of Chongqing University of Technology：Natural Science
基金
重庆市科技攻关项目(CSTC
2011AB4051)
关键词
Ag-La系
稀土相
电子结构
第一性原理
Ag-La system
rare earth phase
electronic structure
first-principle
