Accurate prediction of the properties of materials using the CAM-B3LYP Density Functional

TL;DR

This paper introduces an implementation of the CAM-B3LYP density functional within VASP, demonstrating improved accuracy in predicting material properties and showing competitiveness with advanced ab initio methods.

Contribution

The authors developed and validated a CAM-B3LYP implementation in VASP, enhancing predictive accuracy for materials and enabling comparisons with G0W0 and BSE approaches.

Findings

CAM-B3LYP reduces mean-absolute deviations significantly for lattice parameters and band gaps.

The implementation shows comparable results to G0W0 and BSE methods.

Validated against molecular data with low errors in reaction energies and bond lengths.

Abstract

Density functionals with asymptotic corrections to the long-range potential provide entry-level methods for calculations on molecules that can sustain charge transfer, but similar applications in Materials Science are rare. We describe an implementation of the CAM-B3LYP range-separated functional within the Vienna Ab-initio Simulation Package (VASP) framework, together with its analytical functional derivatives. Results obtained for eight representative materials: aluminum, diamond, graphene, silicon, NaCl, MgO, 2D h-BN and 3D h-BN, indicate that CAM-B3LYP predictions embody mean-absolute deviations (MAD) compared to HSE06 that are reduced by a factor of 6 for lattice parameters, 4 for quasiparticle band gaps, 3 for the lowest optical excitation energies, and 6 for exciton binding energies. Further, CAM-B3LYP appears competitive compared to ab initio G0W0 and Bethe-Salpeter equation (BSE) approaches. The CAM-B3LYP implementation in VASP was verified by comparison of optimized geometries and reaction energies for isolated molecules taken from the ACCDB database, evaluated in large periodic unit cells, to analogous results obtained using Gaussian basis sets. Using standard GW pseudopotentials and energy cutoffs for the plane-wave calculations and the aug-cc-pV5Z basis set for the atomic-basis ones, the MAD in energy for 1738 chemical reactions was 0.34 kcal mol-1, whilst for 480 unique bond lengths this was 0.0036 {\AA}; these values reduced to 0.28 kcal mol-1 (largest error 0.94 kcal mol-1) and 0.0009 {\AA} by increasing the plane-wave cuttoff energy to 850 eV.