Steric Scaling of Hydrogen Transport in FCC Transition Metals for Mechanically Consistent Molecular Dynamics Simulations

Hydrogen diffusion in face-centered cubic metals is examined using replicate-resolved molecular dynamics that quantifies temperature-dependent transport and lattice stability. Transport in Ni, Co and Pd is modeled with a hybrid embedded-atom method/Lennard-Jones framework at 800, 900, 1000, and 1250 K. Rather than fitting hydrogen-metal interactions to a single diffusivity, migration energetics are constrained through steric scaling of the FCC interstitial geometry. All baseline finite-concentration parametrizations remain structurally stable under the monitored lattice-volume criteria. Volume fluctuations stay below 0.15% and swelling below 0.09%. Late-time mean-squared displacement remains linear in all accepted trajectories. Four-temperature Arrhenius fits are stable for Ni, Co, and uniform Pd, while scaled Pd remains less constrained. The expected diffusivity hierarchy D _Pd > D _Co ≈ D _Ni is recovered. Steric scaling lowers Pd diffusivity at every temperature while leaving Ni and Co unchanged, since their interaction parameters are fixed. Pathway-resolved single-H calculations give 0 K barriers of 0.1516 eV for Ni and 0.1294 eV for Co. For Pd, scaling raises the verified static barrier from 0.0234 to 0.0398 eV. A higher-loading Pd test retains the diffusivity reduction while lattice swelling remains bounded. Steric scaling therefore modulates the resolved migration landscape while preserving lattice stability and the observed finite-temperature diffusivity trends.