explain to originate from the stabilities and migration mechanisms associated

Explain to originate from the stabilities and

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explain to originate from the stabilities and migration mechanisms associated with different SIA sites. The accuracy of the ABC-E calculations is validated, in part, by the existing results in the literature for point defect diffusion in hcp Zr, and by benchmarking against analytical results on a hypothetical rough-energy landscape. Lastly, sampling prioritization and computational efficiency are demonstrated through a direct comparison between the ABC-E and the activation relaxation technique. Keywords: atomistic simulation, potential energy landscape, defect migration pathways (Some figures may appear in colour only in the online journal) 0953-8984/14/365402+16$33.00 doi:10.1088/0953-8984/26/36/365402 J. Phys.: Condens. Matter 26 (2014) 365402 (16pp)
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Y Fan et al 2 potential energy surface (PES [ 4 ]). Several atomistic simulation methods have been developed based on biased dynamics and the concept of escaping from deep-energy minima on the PES in static calculations to effectively capture events that would take place over long periods. The family of biased dynamics tech- niques include hyperdynamics [ 5 7 ] and temperature-accel- erated dynamics (TAD [ 8 ]) methods, to boost the rare event transition. In hyperdynamics, a biased potential uni0394 V is added on the system’s PES, and the transition can be boosted by a factor of uni0394 V k T exp[ / ] B . The TAD method speeds up the transitions by increasing the temperature, and then extrapolates to a low- temperature regime, following the Arrhenius behavior, while filtering out the transitions that should not have occurred at the required temperature. Although the hyperdynamics method especially can be very accurate, there are computational chal- lenges in the implementation of the bias potential—i.e. the bias potential must be zero at the dividing surfaces between the minima, and the identification of this bias form requires very high computational load. Recently, significant improve- ments have been made in calculating the bias potential more efficiently using the adaptive boost (AB) method [ 9 , 10 ]. Static approaches that evolve the system on its PES include activation relaxation technique (ART [ 11 , 12 ]), Dimer method [ 13 ], and autonomous basin climbing (ABC) method [ 14 ]. In both the ART and Dimer methods, multiple transition path- ways associated with a given minimum-energy state can be captured, and this is performed by introducing perturbations to the initial state along different directions. Since the pertur- bations are randomly induced, the activation energies for the identified transitions also appear in a random order in this search. All the observed transitions are stored in the reaction catalogue, which serves as the input parameters for the fol- lowing kinetic Monte Carlo (kMC) simulation [ 15 18 ]. The ART and Dimer method have been successfully applied to a series of studies, including the diffusion of point defects [ 13 , 15 19 ], heat release from ion-implanted amorphous Si during its relaxation [ 20 ], and the plastic flow in glassy materials [ 21 ].
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  • Summer '19
  • Transition state, KMC

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