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Citation: A. Nichol, and G.J. Ackland (2016), "Property trends in simple metals: An empirical potential approach", Physical Review B, 93(18), 184101. DOI: 10.1103/physrevb.93.184101.
Abstract: We demonstrate that the melting points and other thermodynamic quantities of the alkali metals can be calculated based on static crystalline properties. To do this we derive analytic interatomic potentials for the alkali metals fitted precisely to cohesive and vacancy energies, elastic moduli, the lattice parameter, and crystal stability. These potentials are then used to calculate melting points by simulating the equilibration of solid and liquid samples in thermal contact at ambient pressure. With the exception of lithium, remarkably good agreement is found with experimental values. The instability of the bcc structure in Li and Na at low temperatures is also reproduced and, unusually, is not due to a soft T1N phonon mode. No forces or finite-temperature properties are included in the fit, so this demonstrates a surprisingly high level of intrinsic transferability in the simple potentials. Currently, there are few potentials available for the alkali metals, so in addition to demonstrating trends in behavior, we expect that the potentials will be of broad general use.

Notes: G.J. Ackland noted that lattice parameters, elastic constants and cohesive energies were used in the fitting process, so the values produced by this conversion should match known values. He noted that bcc crystal structure should be stable and produce a melting temperature of 551 K. Publication information was updated on 12 Oct. 2017. Prior publication listing for this potential was Han, S., Zepeda-Ruiz, L. A., Ackland, G. J., Car, R., and Srolovitz, D. J. (2003). Interatomic potential for vanadium suitable for radiation damage simulations. Journal of Applied Physics, 93(6), 3328. DOI: 10.1063/1.1555275

Moldy FS
Notes: The parameters in Li.moldy were 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 (2016--Nichol-A--Li--LAMMPS--ipr1)
Notes: This conversion was performed by G.J. Ackland and submitted on 8 Dec. 2015.
File(s): superseded

LAMMPS pair_style eam/fs (2016--Nichol-A--Li--LAMMPS--ipr2)
Notes: A new conversion to LAMMPS performed by G.J. Ackland was submitted on 10 Oct. 2017. The previous setfl version above had a spurious oscillation period in the tabulated r*phi function that influenced measurements, most notably static elastic constant evaluations.
Citation: M.M. Islam, A. Ostadhossein, O. Borodin, A. Todd Yeates, W.W. Tipton, R.G. Hennig, N. Kumar, and A.C.T. van Duin (2015), "ReaxFF molecular dynamics simulations on lithiated sulfur cathode materials", Physical Chemistry Chemical Physics, 17(5), 3383-3393. DOI: 10.1039/c4cp04532g.
Abstract: Sulfur is a very promising cathode material for rechargeable energy storage devices. However, sulfur cathodes undergo a noticeable volume variation upon cycling, which induces mechanical stress. In spite of intensive investigation of the electrochemical behavior of the lithiated sulfur compounds, their mechanical properties are not very well understood. In order to fill this gap, we developed a ReaxFF interatomic potential to describe Li–S interactions and performed molecular dynamics (MD) simulations to study the structural, mechanical, and kinetic behavior of the amorphous lithiated sulfur (a-LixS) compounds. We examined the effect of lithiation on material properties such as ultimate strength, yield strength, and Young's modulus. Our results suggest that with increasing lithium content, the strength of lithiated sulfur compounds improves, although this increment is not linear with lithiation. The diffusion coefficients of both lithium and sulfur were computed for the a-LixS system at various stages of Li-loading. A grand canonical Monte Carlo (GCMC) scheme was used to calculate the open circuit voltage profile during cell discharge. The Li–S binary phase diagram was constructed using genetic algorithm based tools. Overall, these simulation results provide insight into the behavior of sulfur based cathode materials that are needed for developing lithium–sulfur batteries.

ReaxFF (2015--Islam-M-M--Li-S--LAMMPS--ipr1)
Notes: This file was sent by Dr. Md Mahbubul Islam (Purdue University) on 2 August 2017 and posted with his permission.
Date Created: October 5, 2010 | Last updated: October 02, 2018