Rotation-induced grain growth and stagnation in phase-field crystal models

Abstract

We consider grain growth and stagnation in polycrystalline microstructures. From the phase-field crystal modeling of the coarsening dynamics, we identify a transition from a grain-growth stagnation upon deep quenching below the melting temperature T(m) to a continuous coarsening at shallower quenching near T(m). The grain evolution is mediated by local grain rotations. In the deep quenching regime, the grain assembly typically reaches a metastable state where the kinetic barrier for recrystallization across boundaries is too large and grain rotation with subsequent coalescence or boundary motion is infeasible. For quenching near T(m), we find that the grain growth depends on the average rate of grain rotation, and follows a power-law behavior with time, with a scaling exponent that depends on the quenching depth.

Nonadiabatic nuclear dynamics of the ammonia cation studied by surface hopping classical trajectory calculations

“…Among the many quasi-classical methods for treating the nonadiabatic nuclear dynamics, e.g., the semiclassical initial-value representation (IVR) [12][13][14][15] , the Ehrenfest dynamics method [16][17][18][19][20] , the frozen Gaussian wavepacket method 21 , the multiple-spawning wave-packet method [22][23][24][25] , to mention a few, the classical trajectory surface-hopping method with its many variants [26][27][28][29][30][31][32][33][34][35][36][37][38][39] is one of the most widely used mixed quantum-classical computational methods.…”

Rotation-limited growth of three-dimensional body-centered-cubic crystals

“…In contrast to classical grain growth laws, grain growth are also known to stagnate in time 10 . In two dimensional systems, it has been suggested that the stagnation might be a combination of high kinetic barriers, preventing mass migration across grain boundaries, and a locking of individual grains preventing grain rotation and subsequent lattice alignment 11 .…”

Topological studies related to molecular systems formed during the Big Bang: H3+ as an example

“…The reasons being trifold: (a) Computing their ab-initio values was always considered as being difficult; [8,9] (b) Even having explicit mathematical expressions for the NACTs, the fact they were frequently singular (see Equation (1)), they had to be eliminated from the relevant Schrödinger equation (see, below, Equation (3)). This process introduced further difficulties; (c) The introduction of the (successful) semi-classical trajectory-surface-hopping (TSH) approach [10][11][12][13][14] became the more popular way to study charge transfer (CT) processes an approach that to a certain level avoids the NACTs.…”