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MOLCAS is an ab initio computational chemistry program, developed at Lund University in collaboration with others. Focus in the program is placed on methods for calculating general electronic structures in molecular systems in both ground and excited states. MOLCAS is, in particular, designed to study the potential surfaces of excited states. The current version of MOLCAS is 7.4. Version 7.2 was reviewed in the Journal of the American Chemical Society.
The program covers a wide range of features, including:
- Ab initio Hartree-Fock (HF), Density functional theory (DFT), second order Møller-Plesset perturbation theory, MCSCF, MRCI, CC, CASPT2 wavefunctions and energies
- Analytic gradient geometry optimization based on HF, DFT, CASSCF, and RASSCF wavefunctions
- Choleski decomposition (CD) and Resolution of the identity (RI) techniques for HF, DFT, CASSCF, CC, MBPT2, and CASPT2.
- On-the-fly auxiliary basis function technique, aCD and acCD.
- CD/RI gradients for "pure" DFT functionals.
- Numerical gradient geometry optimization based on CASPT2 wavefunctions.
- Excited state energies for all wavefunctions, and excited optimized geometries from state averaged CASSCF wavefunctions.
- Transition properties in excited states calculated at the CASSCF/RASSCF level, using a unique RASSCF State Interaction Method.
- Solvent effects can be treated by the Onsager spherical cavity model or Polarizable continuum model (PCM).
- Combined QM and molecular mechanics calculations for systems such as proteins and molecular clusters.
- The NEMO procedure for creating intermolecular force fields for MC/MD simulations; these force fields include electrostatics, induction, dispersion, and exchange-repulsion terms and are based on calculations for individual molecules.
- The Molcas INput Generator (MING) is a GUI for alternative graphical generation of MOLCAS input.
See also 
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