Potentials Repository
FAQ
Q: What is the purpose of this project?
A: The purpose of this project is to provide a repository of interatomic potentials for atomistic simulations (e.g. molecular dynamics) with comparison tools and reference experimental and ab-initio data in order to facilitate the evaluation of these potentials for particular applications. Our goal is not to judge that any particular potential is "the best" because the best interatomic potential may depend on the problem being considered. For example, some interatomic potentials which have been fit only to the properties of solid phases may model solid surface properties better than one fit with solid and liquid properties. However, the second potential will probably better represent properties which have a strong liquid contribution (e.g. crystal-melt interfacial properties). Additionally, we are not limiting the repository to a single class of material (e.g. metals), interatomic potential format (e.g. Embedded-Atom Method), or software package. As we obtain interatomic potentials for other materials or in other formats, we will include them with proper modifications to the website.
Q: I have developed a new interatomic potential, and I would like to have it posted. How do I do that?
A: Send the potential to chandler.becker@nist.gov with format and citation information.
Q: I have downloaded an interatomic potential and wish to acknowledge the website in the references. How do I do that?
A: In addition to the citation information for the interatomic potential, please include "NIST Interatomic Potentials Repository: http://www.ctcms.nist.gov/potentials" in the references.
Q: I have included the NIST repository website address (http://www.ctcms.nist.gov/potentials) in my manuscript. What do I do now?
A: Please send an email to chandler.becker@nist.gov which includes the publication information. This will be used to create a list of papers citing the website in order to help us better understand how the website is being used.
Q: What are the potential formats?
A: The interatomic potentials included in the repository represent a variety of formats, depending on what the developers chose to submit. Not all of them are compatible with any particular software package. In some cases, an interatomic potential may be available in more than one format. Due to the range of formats, we are not able to guarantee that the interatomic potentials will work with particular software packages. Rather, we provide the interatomic potentials with appropriate citation information, and it is up to the user to determine whether a potential will work with given software and produce the expected results.
Steve Plimpton has a very nice description of various potential and file formats on the LAMMPS website. These include the Embedded-atom method (EAM) funcfl and setfl formats, as well as Finnis-Sinclair potentials, and more detailed information can be found there. In addition to LAMMPS, the EAM funcfl and setfl formats are compatible with DYNAMO, the molecular dynamics program developed by Daw, et al. (1), though recent versions of LAMMPS have made some modifications to the header information. The EAM/FS format was designed for use of Finnis-Sinclair (2) interatomic potentials within LAMMPS.
The "table" formats are described in the headers of the files. They are pairs of (x,f(x)) values such as (ρ,F(ρ)) as described in the references associated with each interatomic potential.
Q: I've downloaded a file and plotted it, but the graphs don't look like the figures in the paper. Why?
A: There can be several reasons for this. One is file formatting. Different developers and software packages use different data and file formats to present their interatomic potentials.
Even with the same file/data format, invariant transformations in the EAM format mean that different parameterizations of the interatomic potentials can look completely different but yield the same physical properties. This is especially true for alloys. The issue of invariant transformations is discussed in several places. Among them are:
- Y. Mishin, "Interatomic potentials for metals," in Handbook of Materials Modeling, edited by S. Yip (Springer, Dordrect, The Netherlands, 2005), Chap. 2.2, pp. 459-478.
- A.E. Carlsson, "Beyond pair potentials in elemental transition metals and semiconductors," in Solid State Physics, Volume 43, Ehrenreich and Turnbull (eds.) (1990).
Q: Where can I download the LAMMPS molecular dynamics software package?
A: LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) is developed and maintained at Sandia National Laboratories.
DISCLAIMER:
Certain products or interatomic potentials are identified in this website. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the products are necessarily the best available for the purpose.
(1) Daw M.S. and M.I. Baskes, Phys. Rev. Lett. 50, 1285 (1983). Daw M.S. and M.I. Baskes, Phys. Rev. B 29, 6443 (1984).
(2) Finnis M.W. and J.E. Sinclair, Phil. Mag. A 50, 45-55 (1984).