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Faster Exact Exchange for Solids via occ-RI-K: Application to Combinatorially Optimized Range-Separated Hybrid
Joonho Lee1, Adam Rettig2, Xintian Feng3
1Department of Chemistry, Columbia University, New York, New York10027, United States.
Journal of Chemical Theory and Computation
|December 2, 2022
Summary
A new occ-RI-K algorithm speeds up density functional calculations for solids. It helps assess hybrid functionals, finding that some over/underestimate band gaps, indicating a need for better functionals for both solids and molecules.
Area of Science:
- Solid-state physics and quantum chemistry.
- Computational materials science.
- Electronic structure theory.
Background:
- Accurate computation of electronic band gaps in solids is crucial for materials science.
- Hybrid density functionals offer improved accuracy but are computationally expensive.
- Existing methods struggle with efficiency for large basis sets and complex functionals.
Purpose of the Study:
- To develop an efficient algorithm (occ-RI-K) for calculating exact exchange in density functional theory (DFT) for solids.
- To assess the performance of various hybrid density functionals for predicting solid-state band gaps.
- To identify limitations and guide the development of more accurate DFT functionals.
Main Methods:
- Development of the occ-RI-K algorithm utilizing Gaussian planewave (GPW) density fitting.
- Application of the algorithm to 12 hybrid density functionals for 25 simple solids.
- Use of large, uncontracted basis sets and pseudopotentials near the basis set limit.
- System size up to 16 electrons and 350 basis functions with a 6x6x6 k-mesh.
Main Results:
- The occ-RI-K algorithm provides a 1-2 order of magnitude speedup over conventional GPW methods.
- Global hybrid functionals with 20-27% exact exchange show moderate performance (RMSD 0.61-0.77 eV).
- Range-separated hybrids and those with high exact exchange fractions exhibit significant overestimation of band gaps (RMSD up to 4.16 eV).
- Short-range hybrid HSE underestimates band gaps due to lack of long-range exchange.
Conclusions:
- The occ-RI-K algorithm enables efficient, accurate DFT calculations for solids with large basis sets.
- Current hybrid functionals show varying degrees of success in predicting solid-state band gaps, with none performing optimally across the board.
- Further development is needed to create universally accurate hybrid functionals for both molecular and solid-state applications.
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