| 1 |
module dynamics_nose_hoover |
| 2 |
use definitions, ONLY : DP,NDIM |
| 3 |
use constants |
| 4 |
use simulation |
| 5 |
use parameter |
| 6 |
use force_module, ONLY : calc_forces |
| 7 |
use force_utilities, ONLY : check |
| 8 |
use velocity, ONLY : scale_velocities |
| 9 |
use dynamics_utilities, ONLY : evolve_time, sim_status, init_dynamics_loop, & |
| 10 |
DT2,DTSQRT,init_status |
| 11 |
#ifdef MPI |
| 12 |
use mpi_module, ONLY : mpi_allreduce,mpi_comm_world,mpi_err,& |
| 13 |
mpi_double_precision, mpi_sum |
| 14 |
#endif |
| 15 |
|
| 16 |
implicit none |
| 17 |
PRIVATE |
| 18 |
|
| 19 |
|
| 20 |
|
| 21 |
public :: nose_hoover_dynamics |
| 22 |
|
| 23 |
type (sim_status) :: nose_status |
| 24 |
|
| 25 |
|
| 26 |
contains |
| 27 |
|
| 28 |
|
| 29 |
subroutine nose_hoover_dynamics() |
| 30 |
use velocity, ONLY : calc_temp |
| 31 |
|
| 32 |
|
| 33 |
|
| 34 |
logical :: update_nlist |
| 35 |
logical :: do_pot |
| 36 |
logical :: not_done |
| 37 |
logical :: nmflag |
| 38 |
|
| 39 |
integer :: step, i |
| 40 |
|
| 41 |
call init_status(nose_status) |
| 42 |
call init_dynamics_loop( nose_status ) |
| 43 |
|
| 44 |
! Start the main simulation loop. |
| 45 |
|
| 46 |
do_pot = .true. |
| 47 |
not_done = .true. |
| 48 |
nmflag = .false. |
| 49 |
step = 0 |
| 50 |
|
| 51 |
dynamics: do |
| 52 |
if (.not.not_done) exit dynamics |
| 53 |
|
| 54 |
step = step + 1 |
| 55 |
|
| 56 |
|
| 57 |
if (checktemp.and.(mod(step,check_temp_steps).eq.0)) then |
| 58 |
call calc_temp(nose_status%temp) |
| 59 |
if (dabs(nose_status%temp-target_temp).gt.therm_variance) then |
| 60 |
call scale_velocities(target_temp) |
| 61 |
end if |
| 62 |
end if |
| 63 |
|
| 64 |
call hooverb() |
| 65 |
|
| 66 |
call check(update_nlist) |
| 67 |
|
| 68 |
|
| 69 |
if (do_pot) then |
| 70 |
call calc_forces(update_nlist,nmflag,pe = nose_status%pot_e) |
| 71 |
else |
| 72 |
call calc_forces(update_nlist,nmflag) |
| 73 |
endif |
| 74 |
|
| 75 |
|
| 76 |
call hoovera() |
| 77 |
|
| 78 |
call evolve_time(step,nose_status,do_pot,not_done) |
| 79 |
|
| 80 |
|
| 81 |
#ifdef MPI |
| 82 |
call mpi_barrier(mpi_comm_world,mpi_err) |
| 83 |
#endif |
| 84 |
end do dynamics |
| 85 |
|
| 86 |
end subroutine nose_hoover_dynamics |
| 87 |
|
| 88 |
|
| 89 |
subroutine hoovera() |
| 90 |
use velocity, ONLY : remove_cm_momentum,remove_angular_momentum |
| 91 |
|
| 92 |
|
| 93 |
! ** CONSTANT-TEMPERATURE MOLECULAR DYNAMICS USING CONSTRAINT. ** |
| 94 |
! ** ** |
| 95 |
! ** REFERENCES: ** |
| 96 |
! ** ** |
| 97 |
! ** HOOVER, LADD, AND MORAN, PHYS REV LETT 48, 1818, 1982. ** |
| 98 |
! ** EVANS, J CHEM PHYS 78, 3297, 1983. ** |
| 99 |
! ** BROWN AND CLARKE, MOL PHYS, 51, 1243, 1984. ** |
| 100 |
! ** ** |
| 101 |
! ** ROUTINES SUPPLIED: ** |
| 102 |
! ** ** |
| 103 |
! ** SUBROUTINE HOOVERA ( ) ** |
| 104 |
! ** FIRST PART OF MOVE WITH VELOCITY CONSTRAINTS APPLIED. ** |
| 105 |
! ** SUBROUTINE HOOVERB ( DT ) ** |
| 106 |
! ** SECOND PART OF MOVE. ** |
| 107 |
|
| 108 |
|
| 109 |
|
| 110 |
integer :: i, dim |
| 111 |
real( kind = DP) :: ke, v2, instatemp, chi |
| 112 |
real( kind = DP) :: kebar |
| 113 |
|
| 114 |
real( kind = DP ), dimension(ndim) :: v_dim_i |
| 115 |
|
| 116 |
real(kind=DP) :: ke_local |
| 117 |
|
| 118 |
! units for time are femtosec (10^-15 sec) |
| 119 |
! units for distance are angstroms (10^-10 m) |
| 120 |
! units for velocity are angstroms femtosec^-1 |
| 121 |
! units for mass are a.m.u. (1.661 * 10^-27 kg) |
| 122 |
! units for force are kcal mol^-1 angstrom^-1 |
| 123 |
! |
| 124 |
! converter will put the final terms into angstroms. |
| 125 |
! or angstrom/femtosecond. |
| 126 |
|
| 127 |
! converter = 1.0d0/2.390664d3 |
| 128 |
|
| 129 |
|
| 130 |
! first calculate the temperature using the unconstrained velocities: |
| 131 |
|
| 132 |
ke = 0.0E0_DP |
| 133 |
ke_local = 0.0E0_DP |
| 134 |
|
| 135 |
DO i = 1, nlocal |
| 136 |
do dim = 1, ndim |
| 137 |
v_dim_i(dim) = v(dim,i) + (dt2*f(dim,i)/mass(i))*KCALMOL_TO_AMUA2FS2 |
| 138 |
ke_local = ke_local + mass(i)* & |
| 139 |
(v_dim_i(dim)*v_dim_i(dim)) |
| 140 |
enddo |
| 141 |
enddo |
| 142 |
#ifdef MPI |
| 143 |
call mpi_allreduce(ke_local,ke,1,mpi_double_precision, & |
| 144 |
mpi_sum,mpi_comm_world,mpi_err) |
| 145 |
#else |
| 146 |
ke = ke_local |
| 147 |
#endif |
| 148 |
|
| 149 |
|
| 150 |
ke = ke * AMUA2FS2_TO_KCALMOL |
| 151 |
kebar = kcal_to_kj*1000.0e0_DP*ke / real(3*(natoms - 1),DP) / NAVOGADRO |
| 152 |
instatemp = kebar/k_boltz |
| 153 |
|
| 154 |
!write(*,*) 'before, insta = ', instatemp |
| 155 |
|
| 156 |
chi = sqrt(target_temp / instatemp) |
| 157 |
|
| 158 |
! ** CALCULATE THE CONSTRAINED VELOCITIES AT TIME T+DT/2 ** |
| 159 |
|
| 160 |
do i = 1, nlocal |
| 161 |
do dim = 1, ndim |
| 162 |
v(dim,i) = v(dim,i) * (2.0E0_DP * chi - 1.0E0_DP) + & |
| 163 |
chi*dt*(f(dim,i)/mass(i))*KCALMOL_TO_AMUA2FS2 |
| 164 |
enddo |
| 165 |
enddo |
| 166 |
|
| 167 |
if (sim_type == "cluster") then |
| 168 |
call remove_cm_momentum() |
| 169 |
call remove_angular_momentum() |
| 170 |
endif |
| 171 |
|
| 172 |
end subroutine hoovera |
| 173 |
|
| 174 |
|
| 175 |
|
| 176 |
subroutine hooverb( ) |
| 177 |
|
| 178 |
|
| 179 |
! ******************************************************************* |
| 180 |
! ** SECOND PART OF THE CONSTANT TEMPERATURE ALGORITHM ** |
| 181 |
! ** ** |
| 182 |
! ** THIS ADVANCES THE POSITIONS FROM T TO T + DT. ** |
| 183 |
! ******************************************************************* |
| 184 |
|
| 185 |
|
| 186 |
integer i, dim |
| 187 |
! units for time are femtosec (10^-15 sec) |
| 188 |
! units for distance are angstroms (10^-10 m) |
| 189 |
! units for velocity are angstroms femtosec^-1 |
| 190 |
! units for mass are a.m.u. (1.661 * 10^-27 kg) |
| 191 |
! units for force are kcal mol^-1 angstrom^-1 |
| 192 |
|
| 193 |
do i = 1, nlocal |
| 194 |
do dim = 1, ndim |
| 195 |
q(dim,i) = q(dim,i) + dt * v(dim,i) |
| 196 |
enddo |
| 197 |
enddo |
| 198 |
|
| 199 |
end subroutine hooverb |
| 200 |
|
| 201 |
|
| 202 |
end module dynamics_nose_hoover |
