COLUMBUS COLUMBUS - Programs for high-level ab initio molecular electronic structure calculations
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electronic molecular structure molecular structure electronic structure multi-reference calculation

COLUMBUS Description

COLUMBUS - Programs for high-level ab initio molecular electronic structure calculations COLUMBUS is a collection of programs for high-level ab initio molecular electronic structure calculations. The programs are designed primarily for extended multi-reference (MR) calculations on electronic ground and excited states of atoms and molecules.An important feature of COLUMBUS is its flexibility. In addition to standard classes of reference wave functions, such as CAS or RAS, calculations can be performed with selected reference configurations. Single-reference calculations can be solved very efficiently although the multi-reference aspect of COLUMBUS is emphasized.Main features of COLUMBUS:SCF - closed-shell and restricted open-shellMCSCF - general MCSCF with quadratic convergence including state-averagingMR-CISD - direct CI for all single and double excitations from an arbitrary set of reference configurationsMR-ACPF and MR-AQCC - modified MRCISD methods that include iterative size-extensivity correctionsAnalytic gradient for MCSCF, MR-CISD, MR-ACPF and MR-AQCCAnalytic MR-CISD nonadiabatic coupling vectorAutomatic geometry optimization and saddle-point searchesAutomatic searches for minima on the crossing seam (conical intersections)Spin/orbit CIA massively-parallel version of the MR-CISD, MR-AQCC and respective two-electron density program sections. What's New in This Release: Analytic MR-CISD/AQCC gradient for excited states based on state-averaged MCSCF calculations Analytic MR-CISD nonadiabatic coupling vector Automatic searches for minima and saddle points in excited states Automatic searches for minima on the crossing seam (conical intersections) Integration of the GUGA spin-orbit CI program (still in test phase) A massively parallel CI and two-electron density code Enhanced user interface including visualization features via MOLDEN.

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