arXiv subjects

M. J. Rutter

Publications and source records attributed to M. J. Rutter.

2 recordsLinked to original sources

arXiv2023

Pseudopotential contributions to the quadrupole moment in charged periodic systems

There has been much interest over many years in studying charged systems after the artificial imposition of periodic boundary conditions, and correcting for the resulting divergence of the electrostatic energy density. A correction for cubic cells was derived by Makov and Payne in 1995, and its leading error term is of the form $L^{-5}$ for a cube of side $L$. Most modern Density Functional Theory codes use a different treatment of the `Z$α$' energy term to that used by Makov and Payne, resulting in an error term of the form $L^{-3}$ if their correction is used unmodified. This paper shows how the Makov and Payne result can be made consistent with modern practice.

cond-mat.mtrl-sci↗

arXiv2019

Molecules with dipoles in periodic boundary conditions in a tetragonal cell

When a system which contains a dipole, and whose dimensionality is less than three, is studied in a code which imposes periodic boundary conditions in all three dimensions, an artificial electric field arises which keeps the potential periodic. This has an impact on the total energy of the system, and on any other attribute which would respond to an electric field. Simple corrections are known for 0D systems embedded in a cubic geometry, and 2D slab systems. This paper shows how the 0D result can be extended to tetragonal geometries, and that for a particular $c/a$ ratio the correction is zero. It also considers an exponential error term absent from the usual consideration of 2D slab geometries, and discusses an empirical form for this.

cond-mat.mtrl-sci↗