Quantum Monte Carlo Study of Buckled GaAs Monolayer

We have investigated the ground state properties of buckled GaAs monolayer using density functional theory (DFT) and quantum Monte Carlo (QMC) method. Standard first‐principles approaches such as DFT with approximate exchange‐correlation functionals do not describe the correlation effect accurately and hence, usually cannot predict results within the chemical accuracy. In order to accurate evaluation of correlation energy that makes a small but very important contribution to the total energy of an electronic system, the quantum Monte Carlo methods are used which include the correlation effect of electron‐electron using Jastrow function. We found QMC energies are few tenths eV lower than the DFT energies and the buckled GaAs monolayer have direct the band gap of 1.46 eV within DFT calculations, whereas quasiparticle gap is 3.4(8) eV within QMC calculations. We have also calculated the electron affinity and ionization potential as a function of system size.