June 1st, 2011UncategorizedJuan Sebastian Totero Gongora 0 Comments





XFEL sources are extremely revolutionary, and their study requires a revolutionary code, as well. After one year of work, I coded GZILLA, one of the most comprehensive ab-initio simulator ever realized.

GZilla is composed of more than 120000 lines of MPI parallel code. Its analysis capabilities range from DFT ground state, to time-dependent quantum molecular dynamics in the presence of electromagnetic fields of arbitrary form. Time analysis of far-field patterns is also provided. GZilla implementation has been developed by taking into account state-of-the-art methods and algorithms. In particular:

  • Maxwell’s equations are solved by the FDTD technique within a Cartesian Yee grid with time marching Leapfrogging, Uniaxial Perfectly Matched Layers (UPML) and Total Field Scattered Field (TFSF) source formulation. The far-field pattern is calculated by the time-domain technique. Code parallelization is provided through spatial and time domain decompositions.
  • The time evolution of Schrodinger equations is conversely committed to an original, unconditionally stable Crank Nicholson propagator designed with graph theoretical approaches to minimize communications among processors and an original theory of Perfectly Matched Layers (PML) to absorb outgoing electron waves, combined with a Galerkin-based geometric Multigrid. Code parallelization is provided through a spatial domain decomposition strategy.
  • Molecular dynamics equations are solved by a velocity-verlet time stepping algorithm, parallelized by an original communicator splitting technique.
  • The ground state DFT analysis is derived through a Rayleigh Quotient Multigrid (RQMG) eigenvalue solver, within a Self-Consistent Field (SCF) iteration procedure and an original guaranteed-reduction charge-mixing scheme.


For more info on the code, please read Phys. Rev. Lett. 106, 105504 (2011).