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| ORCA (computer program) | |
|---|---|
| Name | ORCA |
| Developer | Fritz A. Hamprecht; Frank Neese; MPI for Chemical Energy Conversion |
| Programming language | C++, Fortran |
| Operating system | Linux, Windows, macOS |
| License | mixed (proprietary and academic) |
ORCA (computer program) is a quantum chemistry software package designed for electronic structure calculations, supporting methods from mean-field to multireference and coupled cluster techniques. It is widely used in academic and industrial research across institutions such as the Max Planck Society, University of Bonn, University of Heidelberg, and national laboratories including Lawrence Berkeley National Laboratory and Argonne National Laboratory. The program interfaces with experimental communities at facilities like the European Synchrotron Radiation Facility and theoretical consortia including the CECAM network.
ORCA provides a comprehensive suite for ab initio and density functional theory calculations, enabling studies of molecular structure, spectra, and reaction mechanisms for systems ranging from small organic molecules to transition metal complexes. It is employed by researchers associated with Royal Society, Deutsche Forschungsgemeinschaft, and industry partners such as BASF and Roche for projects involving catalysis, spectroscopy, and materials modeling. The codebase originated from collaborations among groups led by developers affiliated with MPI for Chemical Energy Conversion and collaborating centers like Universität Konstanz and Fritz-Haber-Institut.
ORCA implements single-reference methods like Hartree–Fock and Kohn–Sham DFT with a variety of exchange-correlation functionals and basis sets (including contracted and segmented basis libraries used in packages like Gaussian (software) and NWChem). It also supports correlated post-Hartree–Fock approaches such as MP2, CCSD(T), and multireference techniques akin to methods developed in programs like MOLPRO and COLUMBUS. Spectroscopic modules cover EPR parameters, NMR chemical shifts, UV/Vis via TD-DFT, and vibrational analyses comparable to features in Q-Chem and DALTON. Relativistic treatments include scalar relativistic Hamiltonians and two-component methods related to approaches in Dirac (program). Embedded in ORCA are solvation models used in computational studies funded by entities like EPSRC and ERC.
The theoretical core leverages algorithmic developments from quantum chemistry literature, including direct SCF algorithms inspired by work at Max-Planck-Institut für Kohlenforschung and efficient integral evaluation techniques paralleling implementations in Libint-using projects. Correlation routines use tensor contraction strategies similar to formulations in RI-MP2 and density fitting approaches akin to methods in TURBOMOLE. Multireference algorithms implement internally contracted formulations comparable to theoretical frameworks advanced at University of Texas at Austin and Weizmann Institute of Science. Linear-scaling ideas in localized orbital methods reflect research associated with Orsay and the Cambridge Crystallographic Data Centre-linked projects.
ORCA is implemented in C++ and Fortran with modular components for integral evaluation, SCF drivers, and correlation modules, following software design practices found in scientific packages like BLAS-leveraging systems and libraries common to MPI (Message Passing Interface)-based parallelization. The code supports shared-memory and distributed-memory execution patterns used in high-performance computing centers such as National Energy Research Scientific Computing Center and Oak Ridge National Laboratory. Plugin-style interfaces allow coupling to visualization tools produced by groups like Avogadro and file converters used in ChemOffice ecosystems.
ORCA accepts text-based input cards resembling conventions used in Gaussian (software) and outputs human- and machine-readable files including formatted checkpoint data and binary matrices compatible with converters to formats used by JChemPaint and molecular viewers like VMD and PyMOL. It reads basis set libraries and auxiliary fitting sets similar to those distributed by EMSL databases and can interoperate with trajectory files produced by molecular dynamics packages such as GROMACS and AMBER via conversion tools.
Benchmarks comparing ORCA to other packages (for example, Gaussian (software), Q-Chem, MOLPRO, TURBOMOLE) demonstrate competitive timings for DFT, MP2, and coupled cluster tasks on multicore clusters and supercomputers like Blue Gene and machines at TSUBAME. Performance tuning leverages optimized BLAS/LAPACK implementations from providers such as Intel and AMD and scales with MPI and OpenMP strategies used in projects supported by PRACE and national supercomputing centers. Memory-efficient algorithms allow large active-space multireference calculations comparable to research outputs from ETH Zurich and EPFL.
ORCA is distributed under an academic license model with commercial arrangements available, managed by developer teams affiliated with European institutions and distributed to users at universities like University of Oxford and corporations including Siemens. Development follows collaborative models similar to academic-industrial partnerships funded by agencies such as European Research Council and DFG, with contributions from researchers at centers like Fachhochschule and international collaborators across United States, Germany, Japan, and China.
Researchers use ORCA in studies of homogeneous catalysis involving Grubbs catalyst-type motifs, bioinorganic systems such as cytochrome P450, photophysical investigations of dyes related to work at Rensselaer Polytechnic Institute, and materials modeling for metal–organic frameworks akin to studies at ETH Zurich. Example workflows include geometry optimizations, transition-state searches for reactions studied at Broad Institute, and spectroscopic property predictions compared against experiments at facilities like the Diamond Light Source and Swiss Light Source.
Category:Computational chemistry software