Geometry optimization using Krylov subspace method|
- Date: 2015/07/10 14:58
- Name: LK
I have been looking at systems containing several hundred atoms, and comparing geometry optimizations between Cluster and Krylov subspace.
For the cluster eigensolver, for all systems the energy decreases steadily as well as the forces at each step.
For the Krylov algorithm, for smaller systems (say less than 200 atoms) I observe very similar behavior to Cluster. But for systems larger than about 200 atoms, the Krylov optimization had overall increasing energy between optimization steps, as if going to a TS, and the forces often increase/decrease erratically.
I have played with the two keywords orderN.HoppingRanges and orderN.KrylovH.order, but it didn't change the behavior (for example, 9.0 Angs and order 1000).
I have looked at both metallic particles and covalent, large band-gap systems, and I saw the same behavior.
I am wondering whether the forces calculated by the Krylov method have less resolution, or whether there is some other parameter that can converge things tighter (for example, I use 10^-6 energy convergence, and 150Rydberg cutoff).
Thank you for your time.