Interaction of nonlinear supratransmission waves with point defects in the Pt3Al crystal: a molecular dynamics study

The interaction of solitary waves excited via nonlinear supratransmission (NST) with point defects in the Pt3Al crystal (L12 superstructure) is studied by molecular dynamics. A harmonic source with a period of 0.1376 ps (a frequency of 7.27 THz, lying inside the phonon band gap) and an amplitude of 0.21 Å, exceeding the supratransmission threshold of 0.12 Å, injects a wave train that reaches a Pt vacancy, an Al vacancy, or a 〈100〉 platinum dumbbell placed 88 Å from the source. Two additional runs — one at a sub-threshold amplitude of 0.06 Å, the other in a defect-free crystal — serve for comparison. The three defects respond distinctly. The Pt vacancy shows a wave-driven displacement of its energized core, by about 2.5 Å during the passage and up to 4 Å within 35 ps, with only a modest core-energy rise (1.03 to 1.1–1.6 eV) and no net energy trapping (below 0.5 eV). The Al vacancy, giving no potential-energy signal in its platinum environment, is monitored by Wigner–Seitz occupancy and remains immobile, likewise without trapping. The 〈100〉 platinum dumbbell is displaced by about 2 Å and, uniquely, acts as an efficient trap of the wave energy, accumulating up to 10 eV by 30 ps (average 5.4 eV) as its core energy rises from 3.11 to 3.4 – 3.9 eV. Below the threshold all cores stay static. The results quantify the athermal, wave-driven displacement of point defects and identify the dumbbell interstitial as an efficient trap for the energy carried by supratransmission waves.