mirror of https://gitlab.com/QEF/q-e.git
243 lines
9.8 KiB
Fortran
243 lines
9.8 KiB
Fortran
!
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! Copyright (C) 2001-2009 Quantum ESPRESSO group
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! Copyright (C) 2009 Brian Kolb, Timo Thonhauser - Wake Forest University
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! This file is distributed under the terms of the
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! GNU General Public License. See the file `License'
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! in the root directory of the present distribution,
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! or http://www.gnu.org/copyleft/gpl.txt .
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!
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!----------------------------------------------------------------------------
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MODULE kernel_table
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!! This module is used to read in the kernel table file
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!! "vdW_kernel_table" and store some of the important parameters. The
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!! top of the vdW_kernel_table file holds the number of q points, the
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!! number of radial points (r) used in the kernel generation, the maximum
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!! value of r used (r is the parameter in the kernel function d=q*r where
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!! q is defined in DION equation 11), and the values of the q points
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!! used. These parameters are stored as public parameters for use in
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!! various routines. This routine also reads the tabulated values of the
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!! Fourier transformed kernel function for each pair of q values (see
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!! SOLER equations 3 and 8). Since these kernel functions need to be
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!! interpolated using splines, the second derivatives of the Fourier
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!! transformed kernel functions (phi_alpha_beta) are also tabulated in
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!! the vdW_kernel_table and are read in here.
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!! This is done in a module because there are quite a few subroutines in
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!! xc_vdW_DF.f90 that require knowledge of the number (identity) of q
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!! points, the maximum value of the radius, and, of course, the tabulated
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!! kernel function and its second derivatives (for spline interpolation).
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!! Putting this routine in a module meas that those routines can just use
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!! kernel_table rather than passing variables around all over the place.
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USE kinds, ONLY : dp
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USE io_files, ONLY : pseudo_dir
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USE constants, ONLY : pi
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use wrappers, ONLY : md5_from_file
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implicit none
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private
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save
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!! Variables to be used by various routines in xc_vdW_DF.f90, declared
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!! public so they can be seen from outside
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! --------------------------------------------------------------------------
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public :: Nqs, Nr_points, r_max, q_mesh, q_cut, q_min, dk
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public :: kernel, d2phi_dk2
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public :: initialize_kernel_table
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public :: vdw_table_name
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public :: vdw_kernel_md5_cksum
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integer :: Nqs, Nr_points !! The number of q points and radial points
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! !! used in generating the kernel phi(q1*r, q2*r)
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! !! (see DION 14-16 and SOLER 3)
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real(dp) :: r_max, q_cut, q_min, dk !! The maximum value of r, the maximum and minimum
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! !! values of q and the k-space spacing of grid points.
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! !! Note that, during a vdW run, values of q0 found
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! !! larger than q_cut will be saturated (SOLER 5) to
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! !! q_cut
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real(dp), allocatable :: q_mesh(:) !! The values of all the q points used
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real(dp), allocatable :: kernel(:,:,:) !! A matrix holding the Fourier transformed kernel function
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! !! for each pair of q values. The ordering is
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! !! kernel(k_point, q1_value, q2_value)
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real(dp), allocatable :: d2phi_dk2(:,:,:) !! A matrix holding the second derivatives of the above
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! !! kernel matrix at each of the q points. Stored as
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! !! d2phi_dk2(k_point, q1_value, q2_value)
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!
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character(len=256) :: vdw_table_name !! If present from input use this name
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CHARACTER(LEN=30) :: double_format = "(1p4e23.14)"
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CHARACTER(len=32) :: vdw_kernel_md5_cksum = 'NOT SET'
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!
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INTEGER, EXTERNAL :: find_free_unit
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! --------------------------------------------------------------------------
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CONTAINS
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!! ###################################################################################
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!! | |
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!! | INITIALIZE_KERNEL_TABLE |
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!! |___________________________|
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!! Subroutine that actually reads the kernel file and stores the parameters. This routine
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!! is called only once, at the start of a vdW run.
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subroutine initialize_kernel_table(inlc)
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integer, INTENT(IN) :: inlc
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integer :: q1_i, q2_i !! Indexing variables
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integer :: kernel_file !! The unit number for the kernel file
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logical :: file_exists !! A variable to say whether
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! !! needed file exists
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character(len=1000) :: kernel_file_name !! The path to the kernel file.
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! !! Although this name must be
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! !! "vdW_kernel_table", this variable
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! !! is used to hold the entire path
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! !! since we check 3 places for it.
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!!write(*,*) "Reading kernel table ... "
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!! Get the unit number for the kernel file
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kernel_file = find_free_unit()
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!!
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!!
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if (TRIM(vdw_table_name)==' ') then
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if (inlc==3) then
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vdw_table_name='rVV10_kernel_table'
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else
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vdw_table_name='vdW_kernel_table'
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endif
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endif
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if (allocated(kernel)) then
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return
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end if
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!! First we check the current directory for the vdW_kernel_table file
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!! If it is not found there it is looked for in the pseudopotential
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!! directory. If it's not there the default kernel file installed
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!! in the PW directory of the PWSCF source is tried. If none of those
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!! exist the code crashes.
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kernel_file_name=vdw_table_name
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inquire(file=kernel_file_name, exist=file_exists)
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!! If the file is found in the current directory we use that one
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!! ------------------------------------------------------------------------------------------
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if (.not. file_exists) then
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!! No "vdW_kernel_table" file in the current directory. Try the pseudopotential directory
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!! -----------------------------------------------------------------------------------------
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kernel_file_name = trim(pseudo_dir)//'/'//vdw_table_name
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inquire(file=kernel_file_name, exist=file_exists)
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if (.not. file_exists) then
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!! Finally, try the default pw_dir/PW/vdW_kernel_table file
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!! --------------------------------------------------------------------------------------
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kernel_file_name = 'DEFAULT_KERNEL_TABLE_FILE'
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inquire(file=kernel_file_name, exist=file_exists)
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if (.not. file_exists) then
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!! No "vdW_kernel_table" file could be found. Time to die.
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call errore('read_kernel_table', 'No \"vdW_kernel_table\" file could be found',1)
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end if
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end if
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end if
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!! Generates the md5 file
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CALL md5_from_file(kernel_file_name, vdw_kernel_md5_cksum)
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!! Open the file to read
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open(unit=kernel_file, file=kernel_file_name, status='old', form='formatted', action='read')
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!! Read in the number of q points used for this kernel file, the
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!! number of r points, and the maximum value of the r point
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read(kernel_file, '(2i5)') Nqs, Nr_points
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read(kernel_file, double_format) r_max
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allocate( q_mesh(Nqs) )
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allocate( kernel(0:Nr_points,Nqs,Nqs), d2phi_dk2(0:Nr_points,Nqs,Nqs) )
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!! Read in the values of the q points used to generate this kernel
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read(kernel_file, double_format) q_mesh
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!! For each pair of q values, read in the function phi_q1_q2(k).
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!! That is, the fourier transformed kernel function assuming q1 and q2
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!! for all the values of r used.
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!! ----------------------------------------------------------------------------------------------
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do q1_i = 1, Nqs
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do q2_i = 1, q1_i
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read(kernel_file, double_format) kernel(0:Nr_points, q1_i, q2_i)
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kernel(0:Nr_points, q2_i, q1_i) = kernel(0:Nr_points, q1_i, q2_i)
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end do
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end do
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!! ----------------------------------------------------------------------------------------------
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!! Again, for each pair of q values (q1 and q2), read in the value
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!! of the second derivative of the above mentiond Fourier transformed
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!! kernel function phi_alpha_beta(k). These are used for spline
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!! interpolation of the Fourier transformed kernel.
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!! -----------------------------------------------------------------------------------------------
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do q1_i = 1, Nqs
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do q2_i = 1, q1_i
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read(kernel_file, double_format) d2phi_dk2(0:Nr_points, q1_i, q2_i)
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d2phi_dk2(0:Nr_points, q2_i, q1_i) = d2phi_dk2(0:Nr_points, q1_i, q2_i)
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end do
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end do
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!! -----------------------------------------------------------------------------------------------
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close(kernel_file)
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!! Define a few more vaiables useful to some of the subroutines in xc_vdW_DF.f90
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!! ------------------------------------------------------------------------------------------------
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q_cut = q_mesh(Nqs)
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q_min = q_mesh(1)
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dk = 2.0D0*pi/r_max
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!! ------------------------------------------------------------------------------------------------
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end subroutine initialize_kernel_table
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!! #################################################################################################
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end MODULE kernel_table
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