If you have spent any time running density functional theory (DFT) calculations, you know the drill: PBE (Perdew-Burke-Ernzerhof) is fast, reliable, and often... wrong. It systematically underestimates band gaps, over-delocalizes electrons, and struggles with strongly correlated materials.
In this post, I’ll break down what HSE06 is, how to set it up in VASP, and when it’s actually worth the pain. HSE06 is a screened hybrid functional. It mixes 25% exact (Hartree-Fock) exchange with 75% PBE exchange at short range, while keeping PBE correlation.
In older VASP versions (pre-6), you needed LHFCALC = .TRUE. and HFSCREEN = 0.2 . In VASP 6+, you can also use HSE06 as a pseudopotential flag, but the manual INCAR approach is safer. Step 2: FFT grids and precision Hybrid functionals are sensitive to the real-space grid. Use high precision: