NWChem is a computational chemistry package designed to run on high-performance parallel supercomputers. Code capabilities include the calculation of molecular electronic energies and analytic gradients using Hartree-Fock self-consistent field (SCF) theory, Gaussian density function theory (DFT), and second-order perturbation theory. For all methods, geometry optimization is available to determine energy minima and transition states. Classical molecular dynamics capabilities provide for the simulation of macromolecules and solutions, including the computation of free energies using a variety of force fields.
NWChem is scalable, both in its ability to treat large problems efficiently, and in its utilization of available parallel computing resources. The code uses the parallel programming tools TCGMSG and the Global Array (GA) library developed at PNNL for the High Performance Computing and Communication (HPCC) grand-challenge software program and the Environmental Molecular Sciences Laboratory (EMSL) Project. NWChem has been optimized to perform calculations on large molecules using large parallel computers, and it is unique in this regard.
This document is intended as an aid to chemists using the code for their own applications. Users are not expected to have a detailed understanding of the code internals, but some familiarity with the overall structure of the code, how it handles information, and the nature of the algorithms it contains will generally be helpful. The following sections describe the structure of the input file, and give a brief overview of the code architecture. All input directives recognized by the code are described in detail, with options, defaults, and recommended usages, where applicable. The appendices present additional information on the molecular geometry and basis function libraries included in the code.
The EMSL Software Agreement stipulates that the use of NWChem will be acknowledged in any publications which use results obtained with NWChem. The acknowledgment should be of the form:
NWChem Version 4.5, as developed and distributed by Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352 USA, and funded by the U. S. Department of Energy, was used to obtain some of these results.
The words ``A modified version of'' should be added at the beginning, if appropriate. Note: Your EMSL Software Agreement contains the complete specification of the required acknowledgment.
Please use the following citation when publishing results obtained with NWChem:
High Performance Computational Chemistry Group, NWChem, A Computational Chemistry Package for Parallel Computers, Version 4.5 (2003), Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
If you use the DIRDYVTST portion of NWChem, please also use the additional citation:
DIRDYVTST, Yao-Yuan Chuang and Donald G. Truhlar, Department of Chemistry and Super Computer Institute, University of Minnesota; Ricky A. Kendall,Scalable Computing Laboratory, Ames Laboratory and Iowa State University; Bruce C. Garrett and Theresa L. Windus, Environmental Molecular Sciences Laboratory, Pacific Northwest Laboratory.
This software comes without warranty or guarantee of support, but we do try to meet the needs of our user community. Please send bug reports, requests for enhancement, or other comments to
When reporting problems, please provide as much information as possible, including:
Users can also subscribe to an electronic mailing list of other users of the code. This is intended as a general forum through which code users can contact one another and the developers, to share experience with the code and discuss problems. Announcements of new releases and bug fixes will also be made to this list.
To subscribe to the user list, send a message to
majordomo@emsl.pnl.govThe body of the message must contain the line
subscribe nwchem-users
The automated list manager is capable of recognizing a number of commands, including ; ``subscribe'', ``unsubscribe'', ``get'', ``index'', ``which'', ``who'', ``info'' and ``lists''. The command ``end'' halts processing of commands. It will provide some help if the message includes the line help in the body.
Messages can be posted to the list by sending mail to nwchem-users@emsl.pnl.gov. Users are encouraged to report problems to the support address rather than the mailing list, since the support address (listed at the beginning of this section) interfaces to an automated bug tracking mechanism.