NWChem 5.1 Functionality and Capabilities
NWChem provides many methods to compute the properties of
molecular and
periodic systems using standard quantum mechanical descriptions of the
electronic wavefunction or density. In addition, NWChem has the
capability to perform classical molecular dynamics and free energy
simulations. These approaches may be combined to perform mixed
quantum-mechanics and molecular-mechanics simulations.
NWChem is available on almost all high performance computing
platforms,
workstations, PCs running LINUX, as well as clusters of desktop
platforms or
workgroup servers. NWChem development has been devoted to providing
maximum efficiency on massively parallel processors. It achieves this
performance
on the 1960 processors HP Itanium2 system in the EMSL's MSCF. It has
not been optimized for high performance on single processor desktop
systems.
The following quantum mechanical methods are available to calculate
energies, analytic first derivatives and second derivatives with
respect to atomic
coordinates.
- Self Consistent Field (SCF) or Hartree Fock (RHF, UHF).
- Gaussian Density Functional Theory (DFT), using many local,
non-local (gradient-corrected), and hybrid (local, non-local, and HF)
exchange-correlation potentials (spin-restricted)
with formal N3 and N4 scaling.
- Wide range of supported exchange, correlation, and GGA functionals. Click for the full list.
The following methods are available to calculate energies and analytic
first derivatives with respect to atomic coordinates. Second
derivatives are computed by finite difference of the first derivatives.
- Self Consistent Field (SCF) or Hartree Fock (ROHF).
- Gaussian Density Functional Theory (DFT), using many local,
non-local (gradient-corrected), and hybrid (local, non-local, and HF)
exchange-correlation potentials (spin-unrestricted)
with formal N3 and N4 scaling.
- Spin-orbit DFT (SODFT), using many local and non-local
(gradient-corrected)
exchange-correlation potentials (spin-unrestricted).
- MP2 including semi-direct using frozen core and RHF and UHF
reference.
- Complete active space SCF (CASSCF).
- Constrained DFT (CDFT)
The following methods are available to compute energies only. First
and second derivatives are computed by finite difference of the
energies.
- CCSD, CCSD(T), CCSD+T(CCSD), with RHF reference.
- Selected-CI with second-order perturbation correction.
- MP2 fully-direct with RHF reference.
- Resolution of the identity integral approximation MP2
(RI-MP2), with RHF and UHF reference.
- CIS, TDHF, TDDFT, and Tamm-Dancoff TDDFT for excited states
with RHF, UHF, RDFT, or UDFT reference.
- CCSD(T) and CCSD[T] for closed- and open-shell systems (TCE
module)
- UCCD, ULCCD, UCCSD, ULCCSD, UQCISD, UCCSDT, and UCCSDTQ
with RHF, UHF, or ROHF reference.
- UCISD, UCISDT, and UCISDTQ with RHF, UHF, or ROHF
reference.
- Non-canonical UMP2, UMP3, and UMP4 with RHF or UHF
reference.
- EOM-CCSD, EOM-CCSDT, EOM-CCSDTQ for excitation energies,
transition
moments, and excited-state dipole moments of closed- and open-shell
systems
- CCSD, CCSDT, CCSDTQ for dipole moments of closed- and
open-shell
systems
- Second order approximate coupled-cluster model with singles and
doubles (CC2) for excited states in TCE
The following methods can be used to calculate molecular properties:
- Coupled-cluster linear response available using both restricted and unrestricted references
- Ground-state dynamic polarizabilities at the CCSD and CCSDT levels of theory using the linear response formalism
For all methods, the following operations may be performed:
- Single point energy
- Geometry optimization (minimization and transition state)
- Molecular dynamics on the fully ab initio
potential energy surface
- Numerical first and second derivatives automatically
computed if analytic derivatives are not available
- Normal mode vibrational analysis in cartesian coordinates
- ONIOM hybrid method of Morokuma and co-workers
- Generation of the electron density file for graphical
display
- Evaluation of static, one-electron properties.
- Electrostatic potential fit of atomic partial charges
(CHELPG method with optional RESP restraints or charge constraints)
For closed and open shell SCF and DFT:
- COSMO energies - the continuum solvation `COnductor-like
Screening MOdel' of A. Klamt and G. Schüürmann to describe
dielectric screening effects in solvents.
In addition, automatic interfaces are provided to
- The natural bond orbital (NBO) package
- Python
The following methods for including relativity in quantum chemistry
calculations are available:
- The spin-free one-electron Douglas-Kroll approximation is
available for all quantum mechanical methods and their gradients.
- Dyall's spin-free Modified Dirac Hamiltonian approximation
is available for the Hartree-Fock method and its gradients.
- One-electron spin-orbit effects can be included via
spin-orbit potentials. This option is available for DFT and its
gradients, but has to be run without symmetry.
- Spin-free and spin-orbit zeroth-order relativistic approximation (ZORA) for DFT
Two modules are available to compute the energy, optimize the
geometry, numerical second derivatives, and perform ab initio molecular
dynamics using pseudopotential plane-wave DFT.
- PSPW - (Pseudopotential plane-wave) A gamma point code for
calculating
molecules, liquids, crystals, and surfaces.
- Band - A prototype band structure code for calculating
crystals and surfaces with small band gaps (e.g. semi-conductors and
metals)
With
- Conjugate gradient and limited memory BFGS minimization
- Car-Parrinello (extended Lagrangian dynamics)
- Constant energy and constant temperature Car-Parrinello
simulations
- Fixed atoms in cartesian and SHAKE constraints in
Car-Parrinello
- Pseudopotential libraries
- Hamann and Troullier-Martins norm-conserving
pseudopotentials with optional semicore corrections
- Automated wavefunction initial guess, now with LCAO
- Vosko and PBE96 exchange-correlation potentials
(spin-restricted and unrestricted)
- Orthorhombic simulation cells with periodic and
free space boundary conditions.
- Modules to convert between small and large plane-wave
expansions
- Interface to DRIVER, STEPPER, and VIB modules
- Polarization through the use of point charges
- Mulliken, point charge, DPLOT (wavefunction, density and
electrostatic
potential plotting) analysis
- Fermi smearing added to BAND
- Two-component wavefunctions added to BAND
- HGH spin-orbit potentials added to BAND
- Hilbert decomposed parallel FFT added to BAND
- Car-Parrinello QM/MM added to PSPW
- Wannier orbital generation now works with non-cubic cells
- New parallel decomposition in which both the FFT grid and orbitals are
distributed has been implemented in PSPW
The following functionality is available for classical molecular
simulations:
- 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)
The classical force field includes:
- Effective pair potentials (functional form used in AMBER,
GROMOS, CHARMM, etc.)
- First order polarization
- Self consistent polarization
- Smooth particle mesh Ewald (SPME)
- Twin range energy and force evaluation
- Periodic boundary conditions
- SHAKE constraints
- Consistent temperature and/or pressure ensembles
NWChem also has the capability to combine classical and quantum
descriptions in order to perform:
- Mixed quantum-mechanics and molecular-mechanics (QM/MM)
minimizations and molecular dynamics simulation , and
- Quantum molecular dynamics simulation by using any of the
quantum mechanical methods capable of returning gradients.
By using the DIRDYVTST module of NWChem, the user can write an input
file to the POLYRATE program, which can be used to calculate rate
constants including quantum mechanical vibrational energies and
tunneling
contributions.
The Python programming language has been embedded within NWChem and
many of the high level capabilities of NWChem can be easily combined
and controlled by the user to perform complex operations.
- Global arrays (GA)
- Aggregate Remote Memory Copy Interface (ARMCI)
- Linear Algebra (PeIGS) and FFT
- ParIO
- Memory allocation (MA)
Contact: NWChem Support
Updated: Dec., 2007
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