First-principles Calculation Of Interfacial Bonding Properties Of Ag-Ni(W) Composites

Ag-Ni and Ag-W composite materials are widely used in the field of electrical contact materials due to their good electrical and thermal conductivity,low and stable contact resistance,good welding resistance,and other properties.At present,the research on silver-based electrical contact materials is mainly based on experiments,lacking theoretical guidance for composition design,structure optimization and performance regulation.Therefore,it is necessary to go deep into the atomic and electronic levels to objectively understand the intrinsic properties of materials in essence.The interfacial stability,interfacial energy,electronic structure and interfacial bonding strength of Ag-Ni and Ag-W interfacial systems are studied by first-principles calculations.Firstly,the structure optimization of ideal Ag,Ni,W bulk and its three representative surface structures(100),(110)and(111)were carried out respectively.It is found that the difference between the calculated lattice constants of Ag,Ni and W bulks and the lattice constants obtained by previous calculations or by experiments is small.Among the representative surface structures of Ag,the Ag(111)surface model has a small variation in the atomic layer spacing of each layer and has the lowest surface energy,indicating that this model is the most stable.Moreover,when the atomic layer thickness reaches 5 layers,the variation range of the atomic layer spacing in the Ag core begins to decrease,and the surface energy gradually converges.Secondly,five kinds of Ag-Ni and Ag-W composite interface models with different crystallographic orientation relationships were constructed respectively,and their adhesion work,interface energy,electronic density of states and charge density difference were calculated.The calculation results show that in the Ag-Ni composite interface model,the interface adhesion work of the Ag(100)/Ni(100)model is the largest,which is 1.164J/m~2,and the interface energy is the smallest,which is-2.197J/m~2,this kind of model interface has the best combination effect and the most stable interface.Among the Ag-W composite interface models,Ag(111)/W(111)and Ag(110)/W(111)models are more likely to form stable interfacial bonds.The calculation results of the electronic structure show that the two composite materials are mainly combined by covalent bonds in the interface region,and the interface bonding effect is mainly based on the first layer atoms in the interface region.Finally,tensile simulations were performed for the Ag-Ni and Ag-W composite interface models,respectively.It is found that the Ag-W composite interface model exhibits relatively better tensile mechanical properties than the Ag-Ni composite interface model,and its ideal tensile strength can reach up to 8.754 GPa and elongation can reach 16%.At the same time,the fracture site of the two composites is not at the interface,but occurs in the Ag matrix,because the strength of the matrix Ag is relatively low,and the charge density in the interface area is excessively localized,and the charge density in the Ag matrix caused by reduction.