Numerical Simulation Of Charge Distribution In Hexagonal Boron Nitride

Nanomaterials undergo changes in charge distribution under the action of an external electric field or doped charges,thereby causing changes in their structure and physical properties.This is an interesting physical phenomenon with potentially widespread applications.The common theoretical calculation method for studying the mechanical properties of nanostructures is molecular dynamics simulation.In this type of simulation,the charge distribution on the atom is often assumed to be constant.The usual method used to accurately describe the charge distribution is first-principles calculations based on density functional theory.These two methods are often not used in combination due to the huge difference in their computational cost.Therefore,there is a lack of a model that can accurately describe the changes of nanostructures in response to an external electric field or injected charge.To solve this problem,this paper takes h-BN layered nanomaterials as the research object,and parameterizes the charge dipole(QP)model to calculate the change of h-BN charge distribution under the action of external electric field or doped charge.The computational cost of this model is comparable to that of the classical molecular dynamics model,so it can be used to study the electrostatic-related effects of nanostructures such as electrostriction,electro-deflection,or piezoelectricity.In recent years,people have conducted extensive research on two-dimensional materials(2D).2D h-BN has attracted people’s attention due to its hexagonal lattice structure similar to graphene.After chemical functionalization,h-BN can be used to construct various nano-scale electronic devices,but the problem of charge redistribution caused by chemical functionalization in h-BN materials is still unclear.Based on density functional theory(DFT)calculations,we parameterized the QP model to obtain the atomic characteristic width R value and atomic electronegativity parameters suitable for h-BN materials.Then,we used this model to predict the doped charge distribution in h-BN nanosheets of different geometric sizes.The results show that the charge density at the edge of h-BN nanosheets is relatively large.When the global doped charge density in the h-BN nanosheets is constant,the edge charge density was found to be higher for larger layers along the x direction and y direction.In addition,we also calculated the charge enhancement effect of h-BN using the QP model.We found that in-plane charge enhancement factors of h-BN nanosheets increase sublinearly with the length increase of nanosheets in the x direction.In the two different stacking modes of multilayer h-BN nanoribbons,the charge enhancement factors along the x direction of h-BN nanoribbons all increase roughly linearly with the increase of the layers number.The change in charge enhancement factors was not significant when switching between AA and AB stacking.This shows that the stacking method has minor effect on the charge distribution in h-BN.Finally,the QP model was re-parameterized to predict the influence of the external electric field on the intrinsic charge distribution of h-BN.Through a comparison of DFT calculation data and QP model calculation data,it is shown that the QP model could predict the field-induced charges distribution in h-BN nanosheets of different geometries,and the quantity of the polarized charge is highly sensitive to the dimension of the nanosheets in the direction of the applied electric field.