Development Of Interatomic Potentials For Diamond-like Boron-Carbon Structures

Boron is taken as one substitutional impurity,which not only makes diamond exhibit p-type conductive ability,but also enhance the abilities of resistance to oxidation and non-reaction to ferrous materials. Especially the diamond-like C-B materials with excellent optical,electrical and mechanical performances are considered to be a promising superhard conductive materials.A limited amount of boron has been successfully introduced in diamond lattice by different experimental techniques,but the C-B materials with different crystal structures and C:B ratio present a large phase space,which is too wide to be covered by experimental methods.This requires effective interatomic potentials to performe atomistic simulations to provide the details on atomic scale.Therefore in this paper the zincblende-type C-B is taken as the object-orientated material,in which the valid interactions between atoms were described to show the basics of high hardness.The first-princple calculations can give atomic-level results with relatively high precision to understand the bonds connecting the C and B atoms,but the large-scale or systematic simulations requires a large amount of computational resources,which limit the calculations to be performed within the～100atoms on a small time-scale. So the interatomic potentials always play an important role in large-scale atomistic simulations.The previous interatomic potentials in C-B materials were just derived from the combination of Tersoff potentials,for which the non-Tersoff potentials could not be included despite their better description to the C-C bond than Tersoff type.Then the methods are expected to derive the non-Tersoff interatomic potentials of C-B materials from simple first-principle calculations.In this paper,based on Chen-Mobius lattice inversion,the total-energy curves were firstly obtained for zincblend and rocksalt C-B materials by first-principle calculations,the C-B interatomic potential was consequently derived from the total-energy-difference without pirior potential functional forms.Since the volume-dependant term has to be considered in boron-doped diamond, according to the embedded-atomic model,the Finnis-Sinclair C-C potential was also obtained by diamond-structural lattice inversion,and the Stillinger-Weber three-body term was also included to reasonably describe the elastic constants of diamond. Finally the B-B potential curve was also obtained from the cohesive energy of zincblende C-B phase.Based on this set of interatomic potentials,the static mechanical properties were firstly calculated,and the different mechanical moduli were also presented under high pressures. And then the hardness of C-B materials was also derived from the Chen XQ’s fomula. Finally the stress-strain curves were presented in detail for several C-B materials with different compositions and structures.These results indicate that the indued boron atoms in diamond lead to the formation of C-B and B-B bonds,the C-B bonds exhibit similar ideal strength as that of C-C bonds,but the B-B bonds appearently weaken the binding between C atoms. If the distribution of boron atoms in diamond lattice is reasonable enough to avoid the aggregation of B atoms,the B-B bonds could be excluded,which will achieve the superhard conductive C-B materials.These molecular static mechanics calculations have been demonstrating validity of interatomic potentials,which reasonably explain the hardness of C-B materials.This show that the lattice inversion scheme,used in this paper,could be extended to derive the more precise interatomic potentials for C-B phases except zincblende atomic configuration.