mirror of https://gitlab.com/QEF/q-e.git
143 lines
4.4 KiB
Fortran
143 lines
4.4 KiB
Fortran
!
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! Copyright (C) 2002-2011 Quantum ESPRESSO group
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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 cell_nose
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!------------------------------------------------------------------------------!
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USE kinds, ONLY : DP
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!
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IMPLICIT NONE
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SAVE
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REAL(DP) :: xnhh0(3,3) = 0.0_DP
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REAL(DP) :: xnhhm(3,3) = 0.0_DP
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REAL(DP) :: xnhhp(3,3) = 0.0_DP
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REAL(DP) :: vnhh(3,3) = 0.0_DP
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REAL(DP) :: temph = 0.0_DP ! Thermostat temperature (from input)
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REAL(DP) :: fnoseh = 0.0_DP ! Thermostat frequency (from input)
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REAL(DP) :: qnh = 0.0_DP ! Thermostat mass (computed)
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CONTAINS
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subroutine cell_nose_init( temph_init, fnoseh_init )
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USE constants, ONLY: pi, au_terahertz, k_boltzmann_au
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REAL(DP), INTENT(IN) :: temph_init, fnoseh_init
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! set thermostat parameter for cell
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qnh = 0.0_DP
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temph = temph_init
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fnoseh = fnoseh_init
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if( fnoseh > 0.0_DP ) qnh = 2.0_DP * ( 3 * 3 ) * temph * k_boltzmann_au / &
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(fnoseh*(2.0_DP*pi)*au_terahertz)**2
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return
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end subroutine cell_nose_init
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subroutine cell_nosezero( vnhh, xnhh0, xnhhm )
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real(DP), intent(out) :: vnhh(3,3), xnhh0(3,3), xnhhm(3,3)
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xnhh0=0.0_DP
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xnhhm=0.0_DP
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vnhh =0.0_DP
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return
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end subroutine cell_nosezero
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subroutine cell_nosevel( vnhh, xnhh0, xnhhm, delt )
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implicit none
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REAL(DP), intent(inout) :: vnhh(3,3)
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REAL(DP), intent(in) :: xnhh0(3,3), xnhhm(3,3), delt
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vnhh(:,:)=2.0_DP*(xnhh0(:,:)-xnhhm(:,:))/delt-vnhh(:,:)
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return
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end subroutine cell_nosevel
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subroutine cell_noseupd( xnhhp, xnhh0, xnhhm, delt, qnh, temphh, temph, vnhh )
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use constants, only: k_boltzmann_au
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implicit none
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REAL(DP), intent(out) :: xnhhp(3,3), vnhh(3,3)
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REAL(DP), intent(in) :: xnhh0(3,3), xnhhm(3,3), delt, qnh, temphh(3,3), temph
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integer :: i, j
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do j=1,3
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do i=1,3
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xnhhp(i,j) = 2.0_DP*xnhh0(i,j)-xnhhm(i,j) + &
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(delt**2/qnh)* k_boltzmann_au * (temphh(i,j)-temph)
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vnhh(i,j) =(xnhhp(i,j)-xnhhm(i,j))/( 2.0_DP * delt )
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end do
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end do
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return
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end subroutine cell_noseupd
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REAL(DP) function cell_nose_nrg( qnh, xnhh0, vnhh, temph, iforceh )
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use constants, only: k_boltzmann_au
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implicit none
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REAL(DP) :: qnh, vnhh( 3, 3 ), temph, xnhh0( 3, 3 )
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integer :: iforceh( 3, 3 )
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integer :: i, j
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REAL(DP) :: enij
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cell_nose_nrg = 0.0_DP
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do i=1,3
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do j=1,3
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enij = 0.5_DP*qnh*vnhh(i,j)*vnhh(i,j)+temph*k_boltzmann_au*xnhh0(i,j)
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cell_nose_nrg = cell_nose_nrg + iforceh( i, j ) * enij
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enddo
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enddo
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return
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end function cell_nose_nrg
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subroutine cell_nose_shiftvar( xnhhp, xnhh0, xnhhm )
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! shift values of nose variables to start a new step
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implicit none
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REAL(DP), intent(out) :: xnhhm(3,3)
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REAL(DP), intent(inout) :: xnhh0(3,3)
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REAL(DP), intent(in) :: xnhhp(3,3)
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xnhhm = xnhh0
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xnhh0 = xnhhp
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return
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end subroutine cell_nose_shiftvar
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SUBROUTINE cell_nose_info ( delt )
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use constants, only: au_terahertz, pi
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USE io_global, ONLY: stdout
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USE control_flags, ONLY: tnoseh
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IMPLICIT NONE
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REAL(DP), INTENT (IN) :: delt
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INTEGER :: nsvar
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REAL(DP) :: wnoseh
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IF( tnoseh ) THEN
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!
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IF( fnoseh <= 0.0_DP) &
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CALL errore(' cell_nose_info ', ' fnoseh less than zero ', 1)
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IF( delt <= 0.0_DP) &
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CALL errore(' cell_nose_info ', ' delt less than zero ', 1)
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wnoseh = fnoseh * ( 2.0_DP * pi ) * au_terahertz
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nsvar = ( 2.0_DP * pi ) / ( wnoseh * delt )
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WRITE( stdout,563) temph, nsvar, fnoseh, qnh
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END IF
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563 format( //, &
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& 3X,'cell dynamics with nose` temperature control:', /, &
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& 3X,'Kinetic energy required = ', f10.5, ' (Kelvin) ', /, &
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& 3X,'time steps per nose osc. = ', i5, /, &
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& 3X,'nose` frequency = ', f10.3, ' (THz) ', /, &
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& 3X,'nose` mass(es) = ', 20(1X,f10.3),//)
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RETURN
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END SUBROUTINE cell_nose_info
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!
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!------------------------------------------------------------------------------!
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END MODULE cell_nose
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!------------------------------------------------------------------------------!
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