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Citation: X.W. Zhou, D.K. Ward, J.E. Martin, F.B. van Swol, J.L. Cruz-Campa, and D. Zubia (2013), "Stillinger-Weber potential for the II-VI elements Zn-Cd-Hg-S-Se-Te", Physical Review B, 88(8), 85309. DOI: 10.1103/physrevb.88.085309.
Abstract: Bulk and multilayered thin film crystals of II-VI semiconductor compounds are the leading materials for infrared sensing, γ-ray detection, photovoltaics, and quantum dot lighting applications. The key to achieving high performance for these applications is reducing crystallographic defects. Unfortunately, past efforts to improve these materials have been prolonged due to a lack of understanding with regards to defect formation and evolution mechanisms. To enable high-fidelity and high-efficiency atomistic simulations of defect mechanisms, this paper develops a Stillinger-Weber interatomic potential database for semiconductor compounds composed of the major II-VI elements Zn, Cd, Hg, S, Se, and Te. The potential's fidelity is achieved by optimizing all the pertinent model parameters, by imposing reasonable energy trends to correctly capture the transformation between elemental, solid solution, and compound phases, and by capturing exactly the experimental cohesive energies, lattice constants, and bulk moduli of all binary compounds. Verification tests indicate that our model correctly predicts crystalline growth of all binary compounds during molecular dynamics simulations of vapor deposition. Two stringent cases convincingly show that our potential is applicable for a variety of compound configurations involving all the six elements considered here. In the first case, we demonstrate a successful molecular dynamics simulation of crystalline growth of an alloyed (Cd0.28Zn0.68Hg0.04) (Te0.20Se0.18S0.62) compound on a ZnS substrate. In the second case, we demonstrate the predictive power of our model on defects, such as misfit dislocations, stacking faults, and subgrain nucleation, using a complex growth simulation of ZnS/CdSe/HgTe multilayers that also contain all the six elements considered here. Using CdTe as a case study, a comprehensive comparison of our potential with literature potentials is also made. Finally, we also propose unique insights for improving the Stillinger-Weber potential in future developments.

LAMMPS pair_style sw (2013--Zhou-X-W--Zn-Cd-Hg-S-Se-Te--LAMMPS--ipr1)
Notes: This file was sent by Dr. Xiaowang Zhou (Sandia National Laboratories) and approved for distribution on 11 Sept. 2013. This file is compatible with LAMMPS and is intended to be used for elements and compounds of the Zn-Cd-Hg-S-Se-Te system (II-VI semiconductors).
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Citation: X.W. Zhou, M.E. Foster, F.B. van Swol, J.E. Martin, and B.M. Wong (2014), "Analytical Bond-Order Potential for the Cd-Te-Se Ternary System", The Journal of Physical Chemistry C, 118(35), 20661-20679. DOI: 10.1021/jp505915u.
Abstract: CdTe/CdSe core/shell structured quantum dots do not suffer from the defects typically seen in lattice-mismatched films and can therefore lead to improved solid-state lighting devices as compared to the multilayered structures (e.g., InxGa1–xN/GaN). To achieve these devices, however, the quantum dots must be optimized with respect to the structural details at an atomistic level. Molecular dynamics simulations are effective for exploring nano structures at a resolution unattainable by experimental techniques. To enable accurate molecular dynamics simulations of CdTe/CdSe core/shell structures, we have developed a full Cd–Te–Se ternary bond-order potential based on the analytical formalisms derived from quantum mechanical theories by Pettifor et al. A variety of elemental and compound configurations (with coordination varying from 1 to 12) including small clusters, bulk lattices, defects, and surfaces are explicitly considered during potential parametrization. More importantly, enormous iterations are performed to strictly ensure that our potential can simulate the correct crystalline growth of the ground-state structures for Cd, Te, and Se elements as well as CdTe, CdSe, and CdTe1–xSex compounds during molecular dynamics vapor deposition simulations. Extensive test simulation results clearly indicate that our new Cd–Te–Se potential has unique advantages over the existing literature potential involving Cd, Te, and Se elements.

LAMMPS pair_style bop (2014--Zhou-X-W--Cd-Te-Se--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution and listed as having been created by X.W. Zhou (Sandia)
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Citation: D.K. Ward, X.W. Zhou, B.M. Wong, F.P. Doty, and J.A. Zimmerman (2012), "Analytical bond-order potential for the cadmium telluride binary system", Physical Review B, 85(11), . DOI: 10.1103/physrevb.85.115206.
Abstract: CdTe and Cd1−xZnxTe are the leading semiconductor compounds for both photovoltaic and radiation detection applications. The performance of these materials is sensitive to the presence of atomic-scale defects in the structures. To enable accurate studies of these defects using modern atomistic simulation technologies, we have developed a high-fidelity analytical bond-order potential for the CdTe system. This potential incorporates primary (σ) and secondary (π) bonding and the valence dependence of the heteroatom interactions. The functional forms of the potential are directly derived from quantum-mechanical tight-binding theory under the condition that the first two and first four levels of the expanded Green's function for the σ- and π-bond orders, respectively, are retained. The potential parameters are optimized using iteration cycles that include first-fitting properties of a variety of elemental and compound configurations (with coordination varying from 1 to 12) including small clusters, bulk lattices, defects, and surfaces, and then checking crystalline growth through vapor deposition simulations. It is demonstrated that this CdTe bond-order potential gives structural and property trends close to those seen in experiments and quantum-mechanical calculations and provides a good description of melting temperature, defect characteristics, and surface reconstructions of the CdTe compound. Most importantly, this potential captures the crystalline growth of the ground-state structures for Cd, Te, and CdTe phases in vapor deposition simulations.

LAMMPS pair_style bop (2012--Ward-D-K--Cd-Te--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution and listed as having been created by D. Ward (Sandia)
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Citation: Z.Q. Wang, D. Stroud, and A.J. Markworth (1989), "Monte Carlo study of the liquid CdTe surface", Physical Review B, 40(5), 3129-3132. DOI: 10.1103/physrevb.40.3129.
Abstract: We study the liquid-vapor interface of CdTe by a Monte Carlo technique. The interatomic interactions are modeled by a combination of two-body and three-body potentials, using the form proposed by Stillinger and Weber, but with the parameters fitted to bulk atomization energies, lattice constants, and melting temperatures. The calculated heat of fusion and elastic constants agree well with experiments. The surface tension is calculated with a direct Monte Carlo evaluation of the free energy required to create the surface. The calculated surface tension is found to be about 220 ergs/cm2, in good agreement with experimental estimates. The surface region is found to be Cd rich, even though elemental Cd has a higher surface tension than elemental Te.

LAMMPS pair_style sw (1989--Wang-Z-Q--Cd-Te--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution.
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Citation: D.K. Ward, X. Zhou, B.M. Wong, and F.P. Doty (2013), "A refined parameterization of the analytical Cd-Zn-Te bond-order potential", Journal of Molecular Modeling, 19(12), 5469-5477. DOI: 10.1007/s00894-013-2004-8.
Abstract: This paper reports an updated parameterization for a CdTe bond order potential. The original potential is a rigorously parameterized analytical bond order potential for ternary the Cd–Zn–Te systems. This potential effectively captures property trends of multiple Cd, Zn, Te, CdZn, CdTe, ZnTe, and Cd1-xZnxTe phases including clusters, lattices, defects, and surfaces. It also enables crystalline growth simulations of stoichiometric compounds/alloys from non-stoichiometric vapors. However, the potential over predicts the zinc-blende CdTe lattice constant compared to experimental data. Here, we report a refined analytical Cd–Zn–Te bond order potential parameterization that predicts a better CdTe lattice constant. Characteristics of the second potential are given based on comparisons with both literature potentials and the quantum mechanical calculations.

Notes: This is the second analytical BOP Cd-Zn-Te parameterization.

LAMMPS pair_style bop (2013--Ward-D-K--Cd-Te-Zn--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution and listed as having been created by X.W. Zhou (Sandia)
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Citation: D.K. Ward, X.W. Zhou, B.M. Wong, F.P. Doty, and J.A. Zimmerman (2012), "Analytical bond-order potential for the Cd-Zn-Te ternary system", Physical Review B, 86(24), . DOI: 10.1103/physrevb.86.245203.
Abstract: Cd-Zn-Te ternary alloyed semiconductor compounds are key materials in radiation detection and photovoltaic applications. Currently, crystalline defects such as dislocations limit the performance of these materials. Atomistic simulations are a powerful method for exploring crystalline defects at a resolution unattainable by experimental techniques. To enable accurate atomistic simulations of defects in the Cd-Zn-Te systems, we develop a full Cd-Zn-Te ternary bond-order potential. This Cd-Zn-Te potential has numerous unique advantages over other potential formulations: (1) It is analytically derived from quantum mechanical theories and is therefore more likely to be transferable to environments that are not explicitly tested. (2) A variety of elemental and compound configurations (with coordination varying from 1 to 12) including small clusters, bulk lattices, defects, and surfaces are explicitly considered during parameterization. As a result, the potential captures structural and property trends close to those seen in experiments and quantum mechanical calculations and provides a good description of melting temperature, defect characteristics, and surface reconstructions. (3) Most importantly, this potential is validated to correctly predict the crystalline growth of the ground-state structures for Cd, Zn, Te elements as well as CdTe, ZnTe, and Cd1−xZnxTe compounds during highly challenging molecular dynamics vapor deposition simulations.

Notes: This is the first analytical BOP Cd-Zn-Te parameterization. Notes from Dr. Zhou "This was fitted to a theoretical CdTe lattice constant that is significantly larger than the experimental one. The later version (2013--Ward-D-K-Zhou-X-Wong-B-M-Doty-F-P--Cd-Te-Zn) was fitted to the experimental lattice constant."

LAMMPS pair_style bop (2012--Ward-D-K--Cd-Te-Zn--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution and listed as having been created by X.W. Zhou (Sandia)
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Date Created: October 5, 2010 | Last updated: November 02, 2018