25.2.20 Keywords for Module rirpa

The keyword $rirpa allows to specify the following options,

npoints \(n\)

Number of frequency quadrature points, \(n\) (default is 60).

gausslegendre mapping

Use Gauss–Legendre instead of Clenshaw–Curtis quadrature. mapping defines the mapping function to determine the quadrature abscissae and weights, and may be clenshaw (which combines Gauss–Legendre with Clenshaw–Curtis mapping) or rational. If mapping is omitted, Clenshaw–Curtis mapping is the default. Gauss–Legendre quadrature usually converges more rapidly than Clenshaw–Curtis only, especially for difficult cases such as small gap and open shell systems.

maxitergrid \(n\)

Maximum number of nested Clenshaw–Curtis quadrature iterations. During each iteration, the number of quadrature points doubles. The default is 1; namely, nested quadrature rule is turned off.

gridtol \(\epsilon\)

Convergence criterion for the energy difference between successive nested quadrature iterations. Because of the exponentially convergent Clenshaw–Curtis rule, the quadrature error should be on the order of \(\epsilon^2\) once the nested rule converges. The default is 1d-4.

sigmafunc parametrization

Switch on \(\sigma\)-functional corrections to RPA. Available parametrizations are pbe_s1, pbe_s2, pbe_w1, pbe0_s1, pbe0_s2, pbe0_w1, b3-lyp_w1, tpss_w1; the default is pbe_s1. Implemented for energy and gradient; see [310].

riaxk

Performs perturbative corrections to RPA such as AXK, ACSOSEX, or bare second-order exchange; see [305]. The implementation is full parallelized using OpenMP.

acsosex

By default, the riaxk option triggers an RI-AXK calculation. Adding the acsosex option triggers an RI-ACSOSEX calculation instead.

acsox

trigers an bare second-order exchange correction instead of RI-AXK.

o4riaxk

employs the AO based \(\mathcal{O}(N^4 \ln N)\) RI-AXK algorithm instead of the default MO based \(\mathcal{O}(N^5 \ln N)\) algorithm. The AO based algorithm only becomes more efficient than the MO based algorithm for very large systems with small basis sets.

axktol \(\epsilon\)

basis shell quadruple screening threshold for the AO based RI-AXK algorithm. \(\epsilon\) is defined according to equation (27) in [305]. The default value of \(\epsilon\) is \(10^{-\texttt{scfconv}}\).

nohxx

HF energy calculation is skipped, (HXX = Hartree + eXact (Fock) eXchange). The HXX energy computation in the rirpa module is not parallelized for now. For parallel RI-RPA or RI-AXK energy calculations on large systems, it is recommended to use the nohxx option for rirpa, and then compute the HXX energy separately using the parallel version of ridft or dscf (by removing the $dft keyword block and setting $scfiterlimit 1 in the control file).

rpaprof

Generates profiling output.

rpagrad

Switches on the gradients calculation for RI-RPA.

drimp2

Computes gradients in the direct RI-MP2 limit.

iter \(n\)

Number of GKS iterations, \(n\) (default is 0).

ldiis

Turns on DIIS algorithm for faster convergence of GKS iterations (default is off).

eigshift \(r\)

Adds a shift of \(r\) Hartree to the Kohn–Sham gap to aid in the convergence of difficult small-gap systems (default is 0.0 Hartree).

output \(filename\)

Prints a condensed version of GKS-spRPA relevant output to the \(filename\) (default filename is gksrpa.dat).