# nwchem

High-performance computational chemistry software

Description

NWChem is a computational chemistry program package. It provides methods which are scalable both in their ability to treat large scientific computational chemistry problems efficiently, and in their use of available parallel computing resources from high-performance parallel supercomputers to conventional workstation clusters. NWChem can handle: * Molecular electronic structure methods using gaussian

basis functions for high-accuracy calculations of molecules

* Pseudopotentials plane-wave electronic structure methods for calculating

molecules, liquids, crystals, surfaces, semi-conductors or metals

* Ab-initio and classical molecular dynamics simulations

* Mixed quantum-classical simulations

* Parallel scaling to thousands of processors

Features include:
* Molecular electronic structure methods, analytic second derivatives:

- Restricted/unrestricted Hartree-Fock (RHF, UHF)

- Restricted Density Functional Theory (DFT) using many local,

non-local (gradient-corrected) or hybrid (local, non-local, and HF)

exchange-correlation potentials

* Molecular electronic structure methods, analytic gradients:

- Restricted open-shell Hartree-Fock (ROHF)

- Unrestricted Density Functional Theory (DFT)

- Second-order Moeller-Plesset perturbation theory (MP2), using RHF and UHF

reference

- Complete active space SCF (CASSCF)

- Time-Dependent Density Functional Theory (TDDFT)

* Molecular electronic structure methods, single-point energies:

- MP2 with resolution of the identity integral approximation (RI-MP2) or

spin-component scaled approach (SCS-MP2), using RHF and UHF reference

- Coupled cluster singles and doubles, triples or pertubative triples

(CCSD, CCSDT, CCSD(T)), with RHF and UHF reference

- Configuration interaction (CISD, CISDT, and CISDTQ)

- Second-order approximate coupled-cluster singles doubles (CC2)

- State-specific multireference coupled cluster methods (MRCC)

(Brillouin-Wigner (BW-MRCC) and Mukherjee (Mk-MRCC) approaches)

* Further molecular electronic structure features:

- Geometry optimization including transition state searches, constraints

and minimum energy paths (via the Nudged Elastic Band (NEB) and Zero

Temperature String methods)

- Vibrational frequencies

- Equation-of-motion (EOM)-CCSD, EOM-CCSDT, EOM-CCSD(T), CC2,

Configuration-Interaction singles (CIS), time-dependent HF (TDHF) and

TDDFT, for excited states with RHF, UHF, RDFT, or UDFT reference

- Solvatisation using the Conductor-like screening model (COSMO) for RHF,

ROHF and DFT, including analytical gradients

- Hybrid calculations using the two- and three-layer ONIOM method

- Relativistic effects via spin-free and spin-orbit one-electron

Douglas-Kroll and zeroth-order regular approximations (ZORA) and

one-electron spin-orbit effects for DFT via spin-orbit potentials

* Pseudopotential plane-wave electronic structure:

- Pseudopotential Plane-Wave (PSPW), Projector Augmented Wave (PAW) or band

structure methods for calculating molecules, liquids, crystals, surfaces,

semi-conductors or metals

- Geometry/unit cell optimization including transition state searches

- Vibrational frequencies

- LDA, PBE96, and PBE0 exchange-correlation potentials (restricted and

unrestricted)

- SIC, pert-OEP, Hartree-Fock, and hybrid functionals (restricted and

unrestricted)

- Hamann, Troullier-Martins and Hartwigsen-Goedecker-Hutter norm-conserving

pseudopotentials with semicore corrections

- Wavefunction, density, electrostatic and Wannier plotting

- Band structure and density of states generation

* Car-Parrinello ab-initio molecular dynamics (CPMD):

- Constant energy and constant temperature dynamics

- Verlet algorithm for integration

- Geometry constraints in cartesian coordinates

* Classical molecular dynamics (MD):

- Single configuration energy evaluation

- Energy minimization

- Molecular dynamics simulation

- Free energy simulation (multistep thermodynamic perturbation (MSTP) or

multiconfiguration thermodynamic integration (MCTI) methods with options

of single and/or dual topologies, double wide sampling, and separation-

shifted scaling)

- Force fields providing effective pair potentials, first order

polarization, self consistent polarization, smooth particle mesh Ewald

(SPME), periodic boundary conditions and SHAKE constraints

* Mixed quantum-classical:

- Mixed quantum-mechanics and molecular-mechanics (QM/MM) minimizations and

molecular dynamics simulations

- Quantum molecular dynamics simulation by using any of the quantum

mechanical methods capable of returning gradients.

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