Accelerated molecular dynamics study of theGaAs(001)β2(2×4)/c(2×8)surface

Abstract

We develop an accelerated molecular dynamics method that has several advantages over conventional rare-event methods. We apply our method using a semiempirical Tersoff-Abell potential to understand the disordered structure of the GaAs(001)β2(2 × 4) surface at various temperatures. Our simulations indicate that the selfreconstruction of this surface is mediated by As-row-dimer and As-trench-dimer shifting events that typically occur over microsecond-millisecond times at temperatures of interest and that trench-dimer shifting occurs more rapidly than row-dimer shifting. Our calculations indicate that the equilibrium surface consists of an approximately equal mixture of β2(2 × 4) and c(2 × 8) domains, in agreement with an experimental scanningtunneling microscopy study. Due to strain along the [110] direction, there is a tendency for the surface to form long runs of in-phase As-row-and As-trench dimers. There are weak correlations between As-row-dimer pairs along the [110] direction such that the free energy of the c(2 × 8) surface is slightly lower than that of the β2(2 × 4) surface. This finding is also in agreement with the experiment and indicates the dynamical nature of this important substrate for thin-film growth.

Argon-Beam-Induced Defects in a Silica-Supported Single-Walled Carbon Nanotube

“…Additionally, the Tersoff and derived potentials have been widely compared to other experiments: Lajevardipour et al found that the room-temperature Young modulus of graphene (350 N m –1 ) was in close proximity to the experimental value (340 N m –1 ). Lin and Fichthorn found that the equilibrium surface of GaAs is in agreement with an experimental scanning–tunneling microscopy study. Ruthi et al found that the structural characterization of several III–IV zinc blende compound semiconductors was in excellent agreement with that determined by experiments.…”

DFT study of NO adsorption on pristine graphene

“…4. In this section, electron density difference Dr was dened as follows: r NO-graphene , r graphene , r NO , represents the total electron density of the adsorbed system, the electron density of the pure graphene, and the electron density of free state NO molecule, 39,40 respectively. In the ten sectional views, there were no overlaps of the electron density between a NO molecule and C atom.…”

Merging Metadynamics into Hyperdynamics: Accelerated Molecular Simulations Reaching Time Scales from Microseconds to Seconds

“…The CV-based flexibility of metadynamics, combined with the recent notion that it is able to describe system dynamics correctly, makes it a promising candidate for a more generally applicable bias potential-based accelerated MD method. Various hyperdynamics-based approaches have been developed − precisely for this purpose, but these are usually specifically tailored to the (sub)­class of systems for which they were developed: the bias potential is dependent directly on a property of the studied system. In contrast, the biasing in a more general CV-based method such as metadynamics is dependent only on the CVs used, and applying it to a new system only requires changing the CVs, rather than adapting the overall method.…”