Optimization of Stillinger Weber Potential Parameters for Monolayer ZnS

Area of Science:

• Materials Science
• Computational Chemistry
• Condensed Matter Physics

Background:

• Accurate interatomic potentials are crucial for large-scale molecular dynamics simulations of materials.
• Existing Stillinger-Weber (SW) potentials for Zinc Sulfide (ZnS) are optimized for bulk phases and may not accurately represent monolayer properties.
• Understanding the mechanical and vibrational behavior of 2D ZnS is essential for its application in flexible electronics and nanodevices.

Purpose of the Study:

• To develop and optimize a Stillinger-Weber (SW) interatomic potential specifically for ZnS monolayers.
• To enable reliable large-scale molecular dynamics simulations of ZnS monolayers in planar, disordered, and curved configurations.
• To accurately predict the vibrational, mechanical, and curvature-dependent energetics of ZnS nanomaterials.

Main Methods:

• Utilized the force matching algorithm (POTFIT) to refit SW potential parameters.
• Incorporated density-functional-theory (DFT) forces from diverse finite-temperature trajectories of monolayer ZnS.
• Validated the optimized potential against DFT calculations for phonon dispersion and curvature-dependent strain energy.

Main Results:

• The optimized SW potential yields comparable cohesive energies and lattice constants for various ZnS phases (wurtzite, zinc-blende, 2D).
• Monolayer phonon dispersion closely matches DFT results, with significant correction to optical branches.
• Curvature-law analysis indicates negligible strain in flat ZnS, and curved structures exhibit an effective bending modulus of ~35 eV with stability thresholds around 38-40 Å.

Conclusions:

• The optimized SW potential provides a computationally efficient and reliable model for simulating ZnS monolayers across different geometries.
• The potential accurately captures vibrational, mechanical, and curvature energetics, enhancing its transferability to disordered and curved structures.
• Limitations include the absence of explicit long-range electrostatics and polarization effects in the current model.