Keywords: user

Next: 2. Getting Started Up: user Previous: Contents Contents
Subsections

- 1.1 Citation
- 1.2 User Feedback

# 1. Introduction

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.

# 1.1 Citation

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 4.6, 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:

> Straatsma, T.P.; Aprà, E.; Windus, T.L.; Bylaska, E.J.; de Jong, W.; Hirata, S.; Valiev, M.; Hackler, M.; Pollack, L.; Harrison, R.; Dupuis, M.; Smith, D.M.A; Nieplocha, J.; Tipparaju V.; Krishnan, M.; Auer, A.A.; Brown, E.; Cisneros, G.; Fann, G.; Früchtl, H.; Garza, J.; Hirao, K.; Kendall, R.; Nichols, J.; Tsemekhman, K.; Wolinski, K.; Anchell, J.; Bernholdt, D.; Borowski, P.; Clark, T.; Clerc, D.; Dachsel, H.; Deegan, M.; Dyall, K.; Elwood, D.; Glendening, E.; Gutowski, M.; Hess, A.; Jaffe, J.; Johnson, B.; Ju, J.; Kobayashi, R.; Kutteh, R.; Lin, Z.; Littlefield, R.; Long, X.; Meng, B.; Nakajima, T.; Niu, S.; Rosing, M.; Sandrone, G.; Stave, M.; Taylor, H.; Thomas, G.; van Lenthe, J.; Wong, A.; Zhang, Z.; NWChem, A Computational Chemistry Package for Parallel Computers, Version 4.6 (2004), Pacific Northwest National Laboratory, Richland, Washington 99352-0999, USA.
> High Performance Computational Chemistry: an Overview of NWChem a Distributed Parallel Application, Kendall, R.A.; Aprà, E.; Bernholdt, D.E.; Bylaska, E.J.; Dupuis, M.; Fann, G.I.; Harrison, R.J.; Ju, J.; Nichols, J.A.; Nieplocha, J.; Straatsma, T.P.; Windus, T.L.; Wong, A.T. Computer Phys. Comm., 2000, 128, 260-283 .

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.

# 1.2 User Feedback

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

     nwchem-users@emsl.pnl.gov

When reporting problems, please provide as much information as possible, including:

- detailed description of problem
- site name
- platform you are running on, including
  - vendor name
  - computer model
  - operating system
  - compiler
- input file
- output file

Users can also subscribe to the `nwchem-users@emsl.pnl.gov` electronic mailing list itself. 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.gov

The 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.

Next: 2. Getting Started Up: user Previous: Contents Contents