Improved initial guess for minimum energy path calculations

Abstract

A method is presented for generating a good initial guess of a transition path between given initial and final states of a system without evaluation of the energy. An objective function surface is constructed using an interpolation of pairwise distances at each discretization point along the path and the nudged elastic band method then used to find an optimal path on this image dependent pair potential (IDPP) surface.This provides an initial path for the more computationally intensive calculations of a minimum energy path on an energy surface obtained, for example, by ab initio or density functional theory. The optimal path on the IDPP surface is significantly closer to a minimum energy path than a linear interpolation of the Cartesian coordinates and, therefore, reduces the number of iterations needed to reach convergence and averts divergence in the electronic structure calculations when atoms are brought too close to each other in the initial path. The method is illustrated with three examples: (1) rotation of a methyl group in an ethane molecule, (2) an exchange of atoms in an island on a crystal surface, and (3) an exchange of two Si-atoms in amorphous silicon.In all three cases, the computational effort in finding the minimum energy path with DFT was reduced by a factor ranging from 50% to an order of magnitude by using an IDPP path as the initial path. The time required for parallel computations was reduced even more because of load imbalance when linear interpolation of Cartesian coordinates was used.

Molecular dynamics simulations of ternary PtxPdyAuz fuel cell nanocatalyst growth

“…With a higher number of atoms deposited, the Au atoms always stay on the surface, meaning that in the course of cluster growth, segregation of Au always occurs. DFT-level calculations (see calculational details in Ref [48,49]) performed on 1-2 nm icosahedral Pt nanoclusters show low activation energies for Au-surface segregation, which would be negligible under experimental deposition conditions. Inthese calculations, the Au atom was initially placed in the subsurface layer of the particle and the nudged elastic band pathway calculated for Au moving to the surface.…”

Method for finding mechanism and activation energy of magnetic transitions, applied to skyrmion and antivortex annihilation

“…A better starting configuration can be obtained by carrying out a procedure based on an interpolation of pairwise distances between atoms, the image dependent pair potential (IDPP) method [36], since it prevents atoms from coming too close together and generally gives a path that is closer to an MEP.…”

Nudged elastic band calculations accelerated with Gaussian process regression

“…The MEP is found iteratively, starting from some initial path between the two minima. Most often, a straight line interpolation between the minima has been used to generate the initial path [14], but a better approach is to start with a path that interpolates as closely as possible the distances between neighboring atoms, the so-called image dependent pair potential (IDPP) method [26].…”