Investigation Of Doping Effects On Grain Boundary In Cu Based On High-throughput First-principles

Grain boundaries have the the important effects on materials' properties.The grain boundary segregation engineering is aimed to change the microstructures and chemical conpositions at the grain boundaries by introducing dopants into the boundaries and finally improve the properties of materials.However,the grain boundary segregation engineering involves a lot of alloy systems and the reported results are discrete so that it is difficult to make some summarize the rules behind segregation behaviors.In addition,it is difficult to study grain boundary segregation on electron/atom and other microscopic scales with current testing techniques and large-scale simulation methods.Herein,in this work,we employed the highthrougthput first-principles simulations and took a ?5(310)grain boundary in Cu as the example to investigate the doping effect of different elements on the grain boundary.The symmetric data in this work can provide the theoretical basis for the experiment to select the appropriate dopants.We have firstly inverstigated the segregation ability of nonmetallic impurities and their effects on grain boundary properties.We find that all the nonmetallic impurities will segregate to the boundary and the preferred site depends on the atomic radius of impurities.The grain boundary energy is found decreasing with increasing the atomic radius of nonmetallic impurities.We have also studied the effect of nonmetallic dopants on the grain boundary strength combined the Rice-Wang model and the firstprinciples based tensile test.We find that the strengthening/weakening effect is dominated by the electronic interaction of the nonmetallic impurity and the Cu atoms.The results show that the covalent interaction between B and Cu can increase the grain boundary tensile strength by 1%,while the strong polarity interaction between O and Cu can decrease the tensile strength by 12%.We then have built the grain boundary models with s,p,and d block elements based on the electronic configuration in the periodic table and investigated the effect of metallic dopants on grain boundary energy and strength.The results show that the metallic dopants with a larger atomic radius has the stronger ability to segregate to the grain boundary and reduce the grain boundary energy.The effect of metallic dopants on the grain boundary strength is related to the atomic radius and the electronic structures of dopants.For the mechanical contribution,the embrittlement effect of metallic dopants with a larger atomic radius is more significantly.For the chemical contribution,the weak electronic interactions between the s block metallic dopant and Cu cause the limited effect on the strength.The polar interactions between the p block metallic dopant and Cu will reduce the strength.While the d electronic interaction between the d block metallic dopant and Cu will enhance the strength.We have finally constructed the grain boundary models with both a metallic dopant and a nonmetallic impurity,to study the co-doping effect of these two types of dopants.The results show that the relative spatial position of the metallic dopant and nonmetallic impurity at grain boundary is related to their electronegativity and atomic radius.With the bigger difference in their electronegativity,the metallic dopant and nonmetallic impurity prefer to bond with each other,while when their radius are too large,they prefer to stay far away.The metallic dopant and nonmetallic impurity with the larger atomic radius can be more effectively to fill the excess free volume of the grain boundary,to further reduce the grain boundary energy.The strong electronic interaction between the d electron of metallic dopant and the s/p electrons of nonmetallic impurity will weaken the d electronic interaction between the metallic dopant and Cu atoms,as a result dramatically reduce the strengthening effect.