Overview of the All-order code package

Warning

The all-order code package is legacy code and is no longer actively maintained.

The all-order code package provides corrections to the bare CI Hamiltonian arising from core-electron correlations [1][2]. These corrections are stored as effective one-electron integrals in SGC.CON and two-electron screening integrals in SCRC.CON, which are read by pconf when Ksig > 0.

The package consists of four programs: allcore-ci, valsd-ci, sdvw-ci, and second-cis. The first three compute core, core-valence, and valence-valence all-order excitations, respectively. The fourth, second-cis, computes second-order MBPT corrections over a larger set of orbitals and can be run on its own or after the all-order codes to extend their coverage.

Two levels of approximation are available:

• CI+MBPT — runs only second-cis to compute MBPT corrections over a large set of orbitals. This is the baseline approach when all-order corrections are not needed.

• CI+all-order — runs all four programs: the all-order codes first for core and core-valence correlations at high accuracy, then second-cis which reads the all-order results and extends MBPT coverage to higher orbitals. The combined output provides high-accuracy corrections where all-order is available and MBPT coverage elsewhere.

Both methods require a combined B-spline + DHF basis set described in Basis for CI+all-order and CI+MBPT. The typical workflow is to first run the all-order codes (allcore-ci, valsd-ci, sdvw-ci), then run second-cis last to extend MBPT coverage to higher orbitals, optionally reading the all-order results where available, as described in All-order package.

References

[1]

M. S. Safronova, M. G. Kozlov, W. R. Johnson, and D. Jiang. Development of a configuration-interaction plus all-order method for atomic calculations. Phys. Rev. A, 2009.

[2]

S. G. Porsev, M. S. Safronova, M. G. Kozlov, W. R. Johnson, and D. Jiang. Development of a configuration-interaction plus all-order method for atomic calculations. Phys. Rev. A, 2016.