The Construction Of Nb Metal Interaction Potentials

Niobium and niobium alloys are widely used in medical,superconducting,aerospace and other fields due to the advantages of niobium and niobium alloys.Exploring from the microscopic level is an effective way to know more about the performance of niobium.Molecular dynamics simulation is one of the effective means to explore the microscopic world,it is a thermodynamic calculation method based on Newtonian mechanics,which has been widely used in material science.There are two aspects that have great influence on the accurate performance of molecular dynamics simulation,one is numerical algorithm and the other is the accuracy of the potential function.This paper will mainly construct a reliable interatomic interaction potential to reproduce the related physical properties of metal niobium.This paper first review the development of interatomic potentials and the types of interatomic potentials.Then,the interatomic potential of metal niobium has been constructed based on the EAM model,and the cutoff distance is selected between the fifth and sixth neighbors.According to the results of the first principle of Enrico Clementine and Carla Roetti,the parameters of the electron density function in the potential function constructed in this paper are fitted by the least square method.The experimental values of the lattice constants,the cohesive energy,the vacancy formation energy and the elastic constants are used as the fitting data,the undetermined parameters of the pair potential function and the embedded energy function were fitted using the minimum mean square method to determine the final expression of the interatomic potential function.In this paper,we also use the interatomic potential function to calculate the fitting parameters,bulk modulus and average shear modulus,the results are in good agreement with the experimental values.In this paper,the reliability and rationality of the constructed interatomic potential function is verified by two aspects.In the first aspect,the E-r relationship of the potential function is compared with the universal equation of state proposed by Rose,and find that the two are almost identical;The second aspect is to use the potential function to calculate the stability of the three structures under the same volume condition,and the result is that the bcc structure is the most stable,which is consistent with the actual situation.As an application of interatomic potentials,the point defect performance of Nb is calculated by using the potential function constructed in this paper.The calculated mono-vacancy formation energies of Nb in this paper are in good agreement with the experimental data and other authors'calculation results.In this paper,the di-vacancy formation energy and the di-vacancy binding energies in the three configurations are calculated.The three configurations are the distance between the two vacancies from the first,second,and third neighbors,the vacancy formation energy of the three configurations is very close.The first configuration is the smallest formation energy,followed by the second configuration,which is slightly larger than the first configuration.The results of the vacancy binding energy are all greater than zero,indicating that they all have the possibility of existence,in proper order is (?),indicating that the first configuration is the most stable,followed by the second configuration.The above results are consistent with the reported conclusions.