COLUMBUS
Encyclopedia
COLUMBUS is a computational chemistry
software suite for calculating ab initio
molecular electronic structures, designed as a collection of individual programs communicating through files. The programs focus on extended multi-reference calculations of atomic and molecular ground and excited states. Besides standard classes of reference wave functions such as CAS
and RAS, calculations can be performed with selected configurations. It makes use of the atomic orbital integrals and gradient routines from the DALTON
program. The program is available free of charge under license (including the DALTON license).
Computational chemistry
Computational chemistry is a branch of chemistry that uses principles of computer science to assist in solving chemical problems. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids...
software suite for calculating ab initio
Ab initio quantum chemistry methods
Ab initio quantum chemistry methods are computational chemistry methods based on quantum chemistry. The term ab initiowas first used in quantum chemistry by Robert Parr and coworkers, including David Craig in a semiempirical study on the excited states of benzene.The background is described by Parr...
molecular electronic structures, designed as a collection of individual programs communicating through files. The programs focus on extended multi-reference calculations of atomic and molecular ground and excited states. Besides standard classes of reference wave functions such as CAS
Complete active space
In quantum chemistry, a complete active space is a type of classification of molecular orbitals. Spatial orbitals are classified as belonging to three classes:* core, always hold two electrons* active, partially occupied orbitals...
and RAS, calculations can be performed with selected configurations. It makes use of the atomic orbital integrals and gradient routines from the DALTON
DALTON
Dalton is an ab initio quantum chemistry software program. It is capable of calculating various molecular properties using the Hartree–Fock, MP2, MCSCF and coupled cluster theories. Version 2.0 of DALTON added support for density functional theory calculations...
program. The program is available free of charge under license (including the DALTON license).
Major features
- Hartree–Fock method (closed-shell and restricted open-shell)
- Multi-configurational self-consistent fieldMulti-configurational self-consistent fieldMulti-configurational self-consistent field is a method in quantum chemistry used to generate qualitatively correct reference states of molecules in cases where Hartree–Fock and density functional theory are not adequate...
(MCSCF) (quadratic convergence and state averaging) - Multi-reference CISDConfiguration interactionConfiguration interaction is a post-Hartree–Fock linear variational method for solving the nonrelativistic Schrödinger equation within the Born–Oppenheimer approximation for a quantum chemical multi-electron system. Mathematically, configuration simply describes the linear combination...
for an arbitrary set of reference configurations - Analytic gradients for MCSCF, MR-CISD, MR-ACPF and MR-AQCC
- Automatic geometry optimization and saddle-point searches
- Spin/orbit configuration interactionConfiguration interactionConfiguration interaction is a post-Hartree–Fock linear variational method for solving the nonrelativistic Schrödinger equation within the Born–Oppenheimer approximation for a quantum chemical multi-electron system. Mathematically, configuration simply describes the linear combination...