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Citation: H. Park, M.R. Fellinger, T.J. Lenosky, W.W. Tipton, D.R. Trinkle, S.P. Rudin, C. Woodward, J.W. Wilkins, and R.G. Hennig (2012), "Ab initio based empirical potential used to study the mechanical properties of molybdenum", Physical Review B, 85(21), 214121. DOI: 10.1103/physrevb.85.214121.
Abstract: Density-functional theory energies, forces, and elastic constants determine the parametrization of an empirical, modified embedded-atom method potential for molybdenum. The accuracy and transferability of the potential are verified by comparison to experimental and density-functional data for point defects, phonons, thermal expansion, surface and stacking fault energies, and ideal shear strength. Searching the energy landscape predicted by the potential using a genetic algorithm verifies that it reproduces not only the correct bcc ground state of molybdenum but also all low-energy metastable phases. The potential is also applicable to the study of plastic deformation and used to compute energies, core structures, and Peierls stresses of screw and edge dislocations.

LAMMPS pair_style meam/spline (2012--Park-H--Mo--LAMMPS--ipr1)
Notes: These files were contributed by Dr. Michael Fellinger (The Ohio State Univ.) and posted with his permission. The file Park_Mo_2012_bcc.in contains a simple script to demonstrate the use of this interatomic potential with LAMMPS. It was tested on the 1Feb2014 version of LAMMPS with USER-MISC enabled.
Citation: X.W. Zhou, R.A. Johnson, and H.N.G. Wadley (2004), "Misfit-energy-increasing dislocations in vapor-deposited CoFe/NiFe multilayers", Physical Review B, 69(14), 144113. DOI: 10.1103/physrevb.69.144113.
Abstract: Recent molecular dynamics simulations of the growth of [Ni0.8Fe0.2/Au] multilayers have revealed the formation of misfit-strain-reducing dislocation structures very similar to those observed experimentally. Here we report similar simulations showing the formation of edge dislocations near the interfaces of vapor-deposited (111) [NiFe/CoFe/Cu] multilayers. Unlike misfit dislocations that accommodate lattice mismatch, the dislocation structures observed here increase the mismatch strain energy. Stop-action observations of the dynamically evolving atomic structures indicate that during deposition on the (111) surface of a fcc lattice, adatoms may occupy either fcc sites or hcp sites. This results in the random formation of fcc and hcp domains, with dislocations at the domain boundaries. These dislocations enable atoms to undergo a shift from fcc to hcp sites, or vice versa. These shifts lead to missing atoms, and therefore a later deposited layer can have missing planes compared to a previously deposited layer. This dislocation formation mechanism can create tensile stress in fcc films. The probability that such dislocations are formed was found to quickly diminish under energetic deposition conditions.

Notes: These are the original files sent by X.W. Zhou (Sandia National Laboratory) and posted with his permission. C.A. Becker (NIST) modified create.f to include the reference in the generated potential files and the EAM.input file for this composition. These files can be used to generate alloy potentials for Cu, Ag, Au, Ni, Pd, Pt, Al, Pb, Fe, Mo, Ta, W, Mg, Co, Ti, and Zr by editing EAM.input. However, as addressed in the reference, these potentials were not designed for use with metal compounds.
File(s): superseded

LAMMPS pair_style eam/alloy (2004--Zhou-X-W--Mo--LAMMPS--ipr1)
Notes: This file was generated by C.A. Becker (NIST) from create.f and posted with X.W. Zhou's (Sandia National Laboratory) permission.
File(s): superseded

Notes: The file Zhou04_create_v2.f is an updated version of create.f modified by L.M. Hale (NIST) following advice from X.W. Zhou (Sandia National Laboratory). This version removes spurious fluctuations in the tabulated functions of the original potential files caused by single/double precision floating point number conflicts.
LAMMPS pair_style eam/alloy (2004--Zhou-X-W--Mo--LAMMPS--ipr2)
Notes: This file was generated by L.M. Hale from Zhou04_create_v2.f on 13 April 2018 and posted with X.W. Zhou's (Sandia National Laboratory) permission. This version corrects an issue with spurious fluctuations in the tabulated functions.
Citation: S. Han, L.A. Zepeda-Ruiz, G.J. Ackland, R. Car, and D.J. Srolovitz (2003), "Interatomic potential for vanadium suitable for radiation damage simulations", Journal of Applied Physics, 93(6), 3328-3335. DOI: 10.1063/1.1555275.
Abstract: The ability to predict the behavior of point defects in metals, particularly interstitial defects, is central to accurate modeling of the microstructural evolution in environments with high radiation fluxes. Existing interatomic potentials of embedded atom method type predict disparate stable interstitial defect configurations in vanadium. This is not surprising since accurate first-principles interstitial data were not available when these potentials were fitted. In order to provide the input information required to fit a vanadium potential appropriate for radiation damage studies, we perform a series of first-principles calculations on six different interstitial geometries and vacancies. These calculations identify the 〈111〉 dumbbell as the most stable interstitial with a formation energy of approximately 3.1 eV, at variance with predictions based upon existing potentials. Our potential is of Finnis–Sinclair type and is fitted exactly to the experimental equilibrium lattice parameter, cohesive energy, elastic constants and a calculated unrelaxed vacancy formation energy. Two additional potential parameters were used to obtain the best fit to the set of interstitial formation energies determined from the first-principles calculations. The resulting potential was found to accurately predict both the magnitude and ordering of the formation energies of six interstitial configurations and the unrelaxed vacancy ground state, in addition to accurately describing the migration characteristics of the stable interstitial and vacancy. This vanadium potential is capable of describing the point defect properties appropriate for radiation damage simulations as well as for simulations of more common crystal and simple defect properties.

Moldy FS
Notes: The parameters in Mo.moldy were obtained from http://homepages.ed.ac.uk/graeme/moldy/moldy.html and posted with the permission of G.J. Ackland.
Citation: G.J. Ackland, and R. Thetford (1987), "An improved N-body semi-empirical model for body-centred cubic transition metals", Philosophical Magazine A, 56(1), 15-30. DOI: 10.1080/01418618708204464.
Abstract: The recently published semi-empirical potentials of Finnis and Sinclair for the metals V, Nb, Ta, Mo and W appear to give unphysical results for properties involving small interatomic separation. This is remedied by adding to the potentials cores fitted to electron gas calculations on dimers. The adjusted potentials are shown to predict a more realistic pressure-volume relationship. Interstitial formation energies are calculated for various configurations, using quenched molecular dynamics and static relaxation. Some preliminary results on interstitial migration are presented.

Notes: The file AckThet.pdf was obtained from http://homepages.ed.ac.uk/graeme/moldy/moldy.html and posted with the permission of G.J. Ackland.
LAMMPS pair_style eam/fs (1987--Ackland-G-J--Mo--LAMMPS--ipr1)
Notes: This implementation has been retracted as it was identified as having an incorrect functional form. It is made available solely for archival purposes.
File(s): retracted

Citation: S.V. Starikov, L.N. Kolotova, A.Y. Kuksin, D.E. Smirnova, and V.I. Tseplyaev (2018), "Atomistic simulation of cubic and tetragonal phases of U-Mo alloy: Structure and thermodynamic properties", Journal of Nuclear Materials, 499, 451-463. DOI: 10.1016/j.jnucmat.2017.11.047.
Abstract: We studied structure and thermodynamic properties of cubic and tetragonal phases of pure uranium and U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. The main attention was paid to the metastable γ0-phase that is formed in U-Mo alloys at low temperature. Structure of γ0-phase is similar to body-centered tetragonal (bct) lattice with displacement of a central atom in the basic cell along [001] direction. Such displacements have opposite orientations for part of the neighbouring basic cells. In this case, such ordering of the displacements can be designated as antiferro-displacement. Formation of such complex structure may be interpreted through forming of short U-U bonds. At heating, the tetragonal structure transforms into cubic γs-phase, still showing ordering of central atom displacements. With rise in temperature, γs-phase transforms to γ-phase with a quasi body-centered cubic (q-bcc) lattice. The local positions of uranium atoms in γ-phase correspond to γs-phase, however, orientations of the central atom displacements become disordered. Transition from γ0 to γ can be considered as antiferro-to paraelastic transition of order-disorder type. \n\nThis approach to the structure description of uranium alloy allows to explain a number of unusual features found in the experiments: anisotropy of lattice at low temperature; remarkably high self-diffusion mobility in γ-phase; decreasing of electrical resistivity at heating for some alloys. In addition, important part of this work is the development of new interatomic potential for U-Mo system made with taking into account details of studied structures.

LAMMPS pair_style adp (2018--Starikov-S-V--U-Mo--LAMMPS--ipr1)
Notes: These files were sent by S.V. Starikov (Joint Institute for High Temperatures, Russian Academy of Sciences) on 3 Dec. 2017 and posted with his permission.
File(s): superseded

LAMMPS pair_style adp (2018--Starikov-S-V--U-Mo--LAMMPS--ipr2)
Notes: This file was recieved by Sergei Starikov on August 2, 2018. He noted: "In the previous version, one function for Mo-Mo interaction had poor smoothing with r=r_cut. This "bug" led to the sake of the energy conservation during high-temperature (or long) calculations for pure Mo or U-Mo alloy. I made an additional check and found a small potential compilation issue leading to this energy drift. I fixed the file, so now it can be safely used with the time-step = 0.5 fs, even for long runs at high temperatures (the test was made for 1500K)."
Citation: D.E. Smirnova, A.Y. Kuksin, S.V. Starikov, V.V. Stegailov, Z. Insepov, J. Rest, and A.M. Yacout (2013), "A ternary EAM interatomic potential for U-Mo alloys with xenon", Modelling and Simulation in Materials Science and Engineering, 21(3), 35011. DOI: 10.1088/0965-0393/21/3/035011.
Abstract: A new interatomic potential for a uranium–molybdenum system with xenon is developed in the framework of an embedded atom model using a force-matching technique and a dataset of ab initio atomic forces. The verification of the potential proves that it is suitable for the investigation of various compounds existing in the system as well as for simulation of pure elements: U, Mo and Xe. Computed lattice constants, thermal expansion coefficients, elastic properties and melting temperatures of U, Mo and Xe are consistent with the experimentally measured values. The energies of the point defect formation in pure U and Mo are proved to be comparable to the density-functional theory calculations. We compare this new U–Mo–Xe potential with the previously developed U and Mo–Xe potentials. A comparative study between the different potential functions is provided. The key purpose of the new model is to study the atomistic processes of defect evolution taking place in the U–Mo nuclear fuel. Here we use the potential to simulate bcc alloys containing 10 wt% of intermetallic Mo and U2Mo.

LAMMPS pair_style eam/alloy (2013--Smirnova-D-E--U-Mo-Xe--LAMMPS--ipr1)
Notes: This file was sent by Daria Smirnova (Joint Institute for High Temperatures, Russian Academy of Sciences) and posted on 14 March 2013 with her permission.
Date Created: October 5, 2010 | Last updated: October 02, 2018