title: 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.
authors.affiliation: QuantumWise A/S, Lersø Parkallé 107, DK-2100 Copenhagen, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Smidstrup
authors.affiliation: Science Institute and Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík, Iceland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Pedersen
authors.affiliation: QuantumWise A/S, Lersø Parkallé 107, DK-2100 Copenhagen, Denmark.
authors.forename: Kurt
authors.initials: K
authors.lastname: Stokbro
authors.affiliation: Science Institute and Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík, Iceland.
authors.forename: Hannes
authors.initials: H
authors.lastname: Jónsson