Stephen Fahy

TL;DR: These experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator–based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.

TL;DR: The path maintaining rhombohedral symmetry in the transition from graphite to diamond which minimizes the energy at each value of the bond length between layers is determined and cross linking of hexagonal-ring carbon compounds leading to local tetrahedral coordination should be favored when the interlayer distance between hexagonal rings is between 2.1 and 2.3 A.

TL;DR: In this paper, the coherent dynamic of phonons in crystalline materials was observed using X-ray free-electron (XFED) laser pulses, which could provide insight into low energy collective excitations in solids and how they interact at a microscopic level to determine the material's macroscopic properties.

TL;DR: The sixfold coordinated structures, simple cubic and \ensuremath{\beta}-tin, are found at low pressure to be kinetically unstable, transforming spontaneously, without an energy barrier, into the cubic diamond structure, suggesting that sixfold coordination of liquid carbon will be unlikely to occur at moderate pressure and temperature.

TL;DR: In this article, the effect of lattice anharmonicity on the phonon dynamics in photoexcited bismuth was investigated and it was shown that the anharmonic contribution to phonon period is negligible for an excitation of 1.25% or less of the valence electrons.