Computer Physics Communications 181 (2010) 1477–1489 Contents lists available at ScienceDirect Computer Physics Communications www.elsevier.com/locate/cpc Feature article NWChem: A comprehensive and scalable open-source solution for large scale molecular simulations ✩ M. Valiev a,∗ , E.J. Bylaska a , N. Govind a , K. Kowalski a , T.P. Straatsma a , H.J.J. Van Dam a , D. Wang a , J. Nieplocha a , E. Apra b , T.L. Windus c , W.A. de Jong a a William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, United States b Oak Ridge National Laboratory, Computational Sciences and Math Division, Oak Ridge, TN 37831, USA c Iowa State University, Department of Chemistry, Ames, IA 50011, USA article info abstract Article history: Received 20 May 2009 Received in revised form 31 March 2010 Accepted 28 April 2010 Available online 13 May 2010 Keywords: NWChem DFT Coupled cluster QMMM Plane wave methods The latest release of NWChem delivers an open-source computational chemistry package with extensive capabilities for large scale simulations of chemical and biological systems. Utilizing a common compu- tational framework, diverse theoretical descriptions can be used to provide the best solution for a given scientific problem. Scalable parallel implementations and modular software design enable efficient uti- lization of current computational architectures. This paper provides an overview of NWChem focusing primarily on the core theoretical modules provided by the code and their parallel performance. Program summary Program title: NWChem Catalogue identifier: AEGI_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEGI_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Open Source Educational Community License No. of lines in distributed program, including test data, etc.: 11 709 543 No. of bytes in distributed program, including test data, etc.: 680 696 106 Distribution format: tar.gz Programming language: Fortran 77, C Computer: all Linux based workstations and parallel supercomputers, Windows and Apple machines Operating system: Linux, OS X, Windows Has the code been vectorised or parallelized?: Code is parallelized Classification: 2.1, 2.2, 3, 7.3, 7.7, 16.1, 16.2, 16.3, 16.10, 16.13 Nature of problem: Large-scale atomistic simulations of chemical and biological systems require efficient and reliable methods for ground and excited solutions of many-electron Hamiltonian, analysis of the potential energy surface, and dynamics. Solution method: Ground and excited solutions of many-electron Hamiltonian are obtained utilizing density-functional theory, many-body perturbation approach, and coupled cluster expansion. These so- lutions or a combination thereof with classical descriptions are then used to analyze potential energy surface and perform dynamical simulations. Additional comments: Full documentation is provided in the distribution file. This includes an INSTALL file giving details of how to build the package. A set of test runs is provided in the examples directory. The distribution file for this program is over 90 Mbytes and therefore is not delivered directly when download or Email is requested. Instead a html file giving details of how the program can be obtained is sent. Running time: Running time depends on the size of the chemical system, complexity of the method, number of cpu’s and the computational task. It ranges from several seconds for serial DFT energy calcu- ✩ This paper and its associated computer program are available via the Computer Physics Communications homepage on ScienceDirect (http://www.sciencedirect.com/ science/journal/00104655). * Corresponding author. E-mail address: marat.valiev@pnl.gov (M. Valiev). 0010-4655/$ – see front matter  2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cpc.2010.04.018