Si Nanowire Mechanical Response — Parametric MD

Parametric sweep: size effect and rate effect on Young's modulus
Young's modulus vs. diameter and strain rate — 16-run parametric sweep
E: 34 → 44 GPa 16 runs (4 × 4) LAMMPS · Tersoff

Parametric MD study of uniaxial tensile deformation in [001] diamond-cubic silicon nanowires, sweeping wire diameter (33–109 Å) and strain rate (10⁸–5×10⁹ s⁻¹) across 16 independent LAMMPS runs. The central finding: Young's modulus is governed by the surface-to-volume ratio, not strain rate. E rises from 34 to 44 GPa as diameter increases — under-coordinated surface atoms in the diamond cubic lattice reduce local stiffness, and their fractional contribution shrinks as the wire thickens. Strain rate changes E by less than 5% at any diameter, confirming rate-independence in this regime. Extrapolation toward bulk [100] Si (E ≈ 130 GPa) is consistent with a surface-fraction-dependent stiffness model, with the remaining gap attributed to a known Tersoff potential limitation in reproducing anisotropic elastic constants C₁₁ and C₁₂.

GitHub

Stress-strain curves across all 16 runs
Smoothed stress-strain curves across all 16 (diameter × strain-rate) combinations. Linear elastic regime used for best-fit E extraction with R² quality control.
Extrapolation of Young's modulus toward bulk Si limit
Extrapolation of E toward the bulk Si [100] limit using surface-fraction and 1/d models. Both models converge to ~47 GPa at zero surface fraction; the remaining gap to 130 GPa isolates the Tersoff potential error.