PoissonFFTKernel

PoissonFFTKernel

Section Hamiltonian::Poisson
Type integer

Defines which kernel is used to impose the correct boundary conditions when using FFTs to solve the Poisson equation. The default is selected depending on the dimensionality and periodicity of the system:
In 1D, spherical if finite, fft_nocut if periodic.
In 2D, spherical if finite, cylindrical if 1D-periodic, fft_nocut if 2D-periodic.
In 3D, spherical if finite, cylindrical if 1D-periodic, planar if 2D-periodic, fft_nocut if 3D-periodic. See C. A. Rozzi et al., Phys. Rev. B 73, 205119 (2006) for 3D implementation and A. Castro et al., Phys. Rev. B 80, 033102 (2009) for 2D implementation.

Options:

• spherical:
  FFTs using spherical cutoff (in 2D or 3D).
  
• cylindrical:
  FFTs using cylindrical cutoff (in 2D or 3D).
  
• planar:
  FFTs using planar cutoff (in 3D).
  
• fft_nocut:
  FFTs without using a cutoff (for fully periodic systems).
  
• multipole_correction:
  The boundary conditions are imposed by using a multipole expansion. Only appropriate for finite systems. Further specification occurs with variables PoissonSolverBoundaries and PoissonSolverMaxMultipole.
  

 call parse_variable(namespace, 'PoissonFFTKernel', default_kernel, this%kernel)