The COLUMBUS PROGRAMS are 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. In addition to standard classes of reference wave functions such as CAS and RAS , calculations can be performed with selected configurations. Some features employ the atomic orbital integrals and gradient routines from the Dalton as well as MOLCAS program suites. COLUMBUS is distributed open-source under the LGPL license.
12-573: The COLUMBUS PROGRAMS are frequently used for nonadiabatic problems because of its ability to calculate MRCI nonadiabatic coupling vector analytically. The COLUMBUS PROGRAMS were started in 1980 in the Department of Chemistry of Ohio State University by Isaiah Shavitt, Hans Lischka and Ron Shepard. The programs pioneered the Graphical Unitary Group Approach (GUGA) for configuration interaction calculations, which
24-458: A previous CI or MRCI calculation) This method has been implemented first by Robert Buenker and Sigrid D. Peyerimhoff in the seventies under the name Multi-Reference Single and Double Configuration Interaction ( MRSDCI ). MRCI was further streamlined in 1988 by Hans-Joachim Werner and Peter Knowles, which made previous MRCI procedures more generalizable. The MRCI method can also be implemented in semi-empirical methods. An example for this
36-493: Is a stub . You can help Misplaced Pages by expanding it . Multireference configuration interaction In quantum chemistry , the multireference configuration interaction ( MRCI ) method consists of a configuration interaction expansion of the eigenstates of the electronic molecular Hamiltonian in a set of Slater determinants which correspond to excitations of the ground state electronic configuration but also of some excited states . The Slater determinants from which
48-400: Is embraced by advanced users. The open style allows new components to be added to the program suite with ease. However, such flexibility also increased the complexity of input file preparation and execution, making it very difficult for new users. This physical chemistry -related article is a stub . You can help Misplaced Pages by expanding it . This article about chemistry software
60-691: Is now available in many other program suites. The programs are named after Columbus, OH . The COLUMBUS PROGRAMS maintain a program unique style that distinguish itself from most other quantum chemistry programs . The program suite is a collection of a number of programs coded in Fortran , each can be executed independently. These programs communicate through files. Perl scripts are provided to prepare input files and to link these programs together to perform common tasks such as single point energy calculation, geometry optimization, normal mode analysis, etc. This style provides very high degree of flexibility which
72-635: Is the OM2/MRCI method developed by Walter Thiel's group. This quantum chemistry -related article is a stub . You can help Misplaced Pages by expanding it . Sigrid D. Peyerimhoff Sigrid Doris Peyerimhoff (born 12 January 1937, in Rottweil ) is a theoretical chemist and Emeritus Professor at the Institute of Physical and Theoretical Chemistry, University of Bonn , Germany . 1988 Gottfried Wilhelm Leibniz-Prize 1994 Cross of Merit of
84-1228: The University of Chicago , the University of Washington , and Princeton University , she returned to Germany and gained her habilitation at the University of Gießen in 1967. She became professor for theoretical chemistry at the University of Mainz in 1970, and at the University of Bonn in 1972. Her contributions have been to the development of ab initio quantum chemical methods, in particular, multireference configuration interaction , and to their application in many fields of physics and chemistry. Particular emphasis has been given to electronically excited states , molecular spectra and photochemistry . Many studies are on atmospheric molecules and ions, their lifetimes in excited states and decomposition due to radiative and non-radiative processes, and on stability and spectra of clusters. Some of her students became well known for their contribution to quantum chemistry, including Bernd Engels , Stefan Grimme , Bernd A. Hess , Christel Marian , Matthias Ernzerhoff and Bernd M. Nestmann . During her career, she received several awards and memberships: She
96-604: The Federal Republic of Germany 2007 Cothenius-Medaille of the Academy of Sciences Leopoldina 2008 Grand Cross of Merit of the Federal Republic of Germany University of Chicago , University of Washington , Princeton University , University of Mainz , After completing her abitur , Peyerimhoff studied physics at the University of Gießen , completing her degree in 1961 and receiving her doctorate under supervision of Bernhard Kockel in 1963. After researching at
108-499: The excitations are performed are called reference determinants . The higher excited determinants (also called configuration state functions (CSFs) or shortly configurations) are then chosen either by the program according to some perturbation theoretical ansatz according to a threshold provided by the user or simply by truncating excitations from these references to singly, doubly, ... excitations resulting in MRCIS, MRCISD, etc. For
120-423: The ground state using more than one reference configuration means a better correlation and so a lower energy. The problem of size inconsistency of truncated CI-methods is not solved by taking more references. As a result of a MRCI calculation one gets a more balanced correlation of the ground and excited states . For quantitative good energy differences (excitation energies) one has to be careful in selecting
132-514: The neglect of other dominant configurations of the excited states which are still uncorrelated. Selecting the references can be done manually ( Φ 1 , Φ 2 , Φ 5 , . . . {\displaystyle \Phi _{1},\Phi _{2},\Phi _{5},...} ), automatically (all possible configurations within an active space of some orbitals) or semiautomatically (taking all configurations as references that have been shown to be important in
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#1732786625382144-501: The references. Taking only the dominant configuration of an excited state into the reference space leads to a correlated (lower) energy of the excited state. The generally too-high excitation energies of CIS or CISD are lowered. But usually excited states have more than one dominant configuration and so the ground state is more correlated due to: a) now including some configurations with higher excitations (triply and quadruply in MRCISD); b)
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