GRID_OPTIMIZATION
Optimizes RI-RS grids using small local atomic environments. For every atom in the structure, a cluster is formed from all atoms whose distance from the centre atom is smaller than CUTOFF_ATOMIC_CLUSTER. All three-centre integrals within each cluster are computed analytically and serve as exact reference values. The grid points are optimized such that the corresponding RI-RS three-centre integrals reproduce these references. For a cluster \(C_I\), the normalized squared RI-RS error is \(E_I = \frac{1}{N_I} \sum_{P\mu\nu \in C_I} \left|(\mu\nu|P) - \sum_{\mathbf{r}_{A\ell} \in C_I} \varphi_\mu(\mathbf{r}_{A\ell}) \varphi_\nu(\mathbf{r}_{A\ell}) Z_{A\ell P}\right|^2\). The total objective is the average over all local clusters, \(E_\mathrm{loc} = \frac{1}{N_\mathrm{at}} \sum_{I=1}^{N_\mathrm{at}} E_I\). Starting from pre-tabulated atom-specific grids, the optimization adapts the grid to the chemical environment and composition of the structure and can permit substantially smaller grids. Compact grids often work well for small basis sets, but the point count specified with GRID_SIZE or N_POINT_PERCENTAGE should be tuned and converged for the chosen basis sets and chemical system. [Edit on GitHub]
Keywords
Keyword descriptions
- CUTOFF_ATOMIC_CLUSTER
Type: real
Default: 3.00000000E+000 [angstrom]
Usage: CUTOFF_ATOMIC_CLUSTER [angstrom] 3.0Description: Radius of the atom-centred cluster used to construct the local three-centre integral fitting objective. Atoms within this distance of the centre atom are included. [Edit on GitHub]
- GRID_SIZE
Type: string[2]
Repeatable: yes
Usage: GRID_SIZE Si 100Description: Specifies how many grid points are used per atom for a given element. Repeat this keyword once for every element in the structure. [Edit on GitHub]
- MAX_ITER
Type: integer
Default: 100
Usage: MAX_ITER 100Description: Maximum number of objective-and-gradient evaluations in the single cooperative Cartesian grid optimization. [Edit on GitHub]
- N_POINT_PERCENTAGE
Type: real
Default: -1.00000000E+000
Usage: N_POINT_PERCENTAGE 20Description: The element grids are read from the .ion files selected by GRID_SELECT; GRID_FILE_SUFFIX determines user-provided filenames. From these initial grids, only N_POINT_PERCENTAGE % of each element’s grid points are taken in the actual GW calculation. [Edit on GitHub]