Abstract
The introduction of ultrasoft pseudopotentials transforms the Schrödinger equation into a generalised eigenvalue problem with metric S, and in order to obtain the correct contravariant gradient the inverse of the S-matrix must be applied. We present an analytic derivation of the inverse S-matrix and a Hermitian preconditioning operator suitable for use in ultrasoft schemes. We show how the preconditioner may be calculated semi-analytically and applied without the need to store the matrix explicitly. The new scheme has been implemented within Castep, a plane-wave DFT program, and shown to offer considerable improvements over standard schemes for a set of representative test cases, as well as a SrTiO3 system of particular scientific interest.
Original language | English |
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Pages (from-to) | 24-29 |
Number of pages | 6 |
Journal | Computer Physics Communications |
Volume | 174 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Jan 2006 |
Keywords
- Eigenvalue problem
- Preconditioning;
- Ultrasoft pseudopotentials
- Electronic structure