In , 25% exact exchange is applied across all distances. In a solid, this creates a long-range interaction that is computationally expensive ($O(N^4)$) and physically inappropriate for metals or small-gap semiconductors. HSE06 screens this interaction. At long range, the functional behaves purely like PBE. This makes it suitable for periodic solids and significantly reduces computational cost compared to PBE0. hse06 vasp