FI-2015-1-0008: Real Space Real Time method for first principles calculations of general periodic systems using OCTOPUS


Status: submitted project

We present a real-space method for electronic-structure calculations of systems with general full or partial periodicity. The method is based on the self-consistent solution of the Kohn-Sham equations, using first principles pseudopotentials, on a uniform three-dimensional non-Cartesian grid. Its efficacy derives from the introduction of a new generalized high-order finite-difference method that avoids the numerical evaluation of mixed derivative terms and results in a simple yet accurate finite difference operator. Our method enjoys the main advantages of real-space grid techniques over traditional plane-wave representations for density functional calculations, namely, improved scaling and easier implementation on parallel computers.


We are developing a part of code in the OCTOPUS package which will deal with electronic structure calculations of general periodic systems. In this code, the laplacian will be modified with metric depending upon the lattice structure. To use this approach in the non-orthorhombic unit cells, Laplacian will require O(N^2) neighboring grid points to be evaluated instead of O(N) neighbours in case of cubic unit cells. This increases the computational complexity. Depending on the size of the simulation box, the spacing of real space grid and number of electrons in the unit cells, the computation time of electronic structure calculations vary. We are also planning to implement the laser interactions with solid, which in turn will have time dependent run, which is very time consuming. To have uninteruppted run, we must rely on supercomputing facilities such as MareNostrum.


Angel Rubio
Umberto de Giovannini