kpoint_lattice_fft Module Reference

Batched lattice Fourier transforms for complete regular k-point grids. More...

Functions/Subroutines
logical function, public	regular_kpoint_grid (xkp, nkp_grid, grid_index, k_offset)
	Test and map a complete, uniformly shifted reciprocal grid.
subroutine, public	cell_to_k_grid_fft (values_rs, index_to_cell, xkp, nkp_grid, values_k, used_fft, deriv_direction, hmat, selected_kpoints)
	Transform a batch of real matrices from image cells to every supplied k point.
subroutine, public	k_grid_to_cell_fft (values_k, xkp, nkp_grid, index_to_cell, values_rs, used_fft)
	Transform complete reciprocal-grid data back to image-cell values.

Detailed Description

Batched lattice Fourier transforms for complete regular k-point grids.

  Real-space image cells are folded modulo the reciprocal grid.  Shifted Monkhorst-Pack
  meshes are handled by a phase twist before the FFT.  Non-regular or incomplete k-point
  lists transparently use the direct phase sum.

Function/Subroutine Documentation

regular_kpoint_grid()

logical function, public kpoint_lattice_fft::regular_kpoint_grid	(	real(kind=dp), dimension(:, :), intent(in)	xkp,
		integer, dimension(3), intent(in)	nkp_grid,
		integer, dimension(:, :), intent(out), optional	grid_index,
		real(kind=dp), dimension(3), intent(out), optional	k_offset )

Test and map a complete, uniformly shifted reciprocal grid.

Parameters

xkp	reciprocal coordinates, in units of reciprocal lattice vectors
nkp_grid	regular-grid dimensions
grid_index	FFT-grid index for every k point
k_offset	common reciprocal-coordinate offset

Returns

true for a complete regular grid

Definition at line 49 of file kpoint_lattice_fft.F.

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cell_to_k_grid_fft()

subroutine, public kpoint_lattice_fft::cell_to_k_grid_fft	(	real(kind=dp), dimension(:, :, :), intent(in)	values_rs,
		integer, dimension(:, :), intent(in)	index_to_cell,
		real(kind=dp), dimension(:, :), intent(in)	xkp,
		integer, dimension(3), intent(in)	nkp_grid,
		complex(kind=dp), dimension(:, :, :), intent(out)	values_k,
		logical, intent(out), optional	used_fft,
		integer, intent(in), optional	deriv_direction,
		real(kind=dp), dimension(3, 3), intent(in), optional	hmat,
		integer, dimension(:), intent(in), optional	selected_kpoints )

Transform a batch of real matrices from image cells to every supplied k point.

Parameters

values_rs	real-space matrices; the last dimension enumerates image cells
index_to_cell	integer lattice vector for every image cell
xkp	reciprocal coordinates of all requested k points
nkp_grid	dimensions of the candidate regular reciprocal grid
values_k	complex matrices at every k point
used_fft	reports whether the regular-grid FFT path was used
deriv_direction	optional Cartesian k derivative (1, 2, or 3)
hmat	direct-lattice cell matrix, required for a derivative
selected_kpoints	optional indices of k points to retain in values_k

Definition at line 114 of file kpoint_lattice_fft.F.

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k_grid_to_cell_fft()

subroutine, public kpoint_lattice_fft::k_grid_to_cell_fft	(	complex(kind=dp), dimension(:, :, :), intent(in)	values_k,
		real(kind=dp), dimension(:, :), intent(in)	xkp,
		integer, dimension(3), intent(in)	nkp_grid,
		integer, dimension(:, :), intent(in)	index_to_cell,
		complex(kind=dp), dimension(:, :, :), intent(out)	values_rs,
		logical, intent(out), optional	used_fft )

Transform complete reciprocal-grid data back to image-cell values.

Parameters

values_k	complex matrices on a complete regular reciprocal grid
xkp	reciprocal coordinates, in units of reciprocal lattice vectors
nkp_grid	dimensions of the reciprocal grid
index_to_cell	integer lattice vector for every requested image cell
values_rs	reconstructed complex matrices in the requested image cells
used_fft	reports whether the regular-grid FFT path was used

Definition at line 258 of file kpoint_lattice_fft.F.

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