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chuckv |
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module dynamics_nose_hoover |
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use definitions, ONLY : DP,NDIM |
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use constants |
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use simulation |
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use parameter |
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use force_module, ONLY : calc_forces |
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use force_utilities, ONLY : check |
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use velocity, ONLY : scale_velocities |
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use dynamics_utilities, ONLY : evolve_time, sim_status, init_dynamics_loop, & |
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DT2,DTSQRT,init_status |
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#ifdef MPI |
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use mpi_module, ONLY : mpi_allreduce,mpi_comm_world,mpi_err,& |
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mpi_double_precision, mpi_sum |
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#endif |
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implicit none |
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PRIVATE |
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public :: nose_hoover_dynamics |
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type (sim_status) :: nose_status |
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contains |
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subroutine nose_hoover_dynamics() |
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use velocity, ONLY : calc_temp |
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logical :: update_nlist |
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logical :: do_pot |
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logical :: not_done |
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logical :: nmflag |
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integer :: step, i |
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call init_status(nose_status) |
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call init_dynamics_loop( nose_status ) |
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! Start the main simulation loop. |
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do_pot = .true. |
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not_done = .true. |
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nmflag = .false. |
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step = 0 |
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dynamics: do |
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if (.not.not_done) exit dynamics |
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step = step + 1 |
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if (checktemp.and.(mod(step,check_temp_steps).eq.0)) then |
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call calc_temp(nose_status%temp) |
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if (dabs(nose_status%temp-target_temp).gt.therm_variance) then |
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call scale_velocities(target_temp) |
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end if |
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end if |
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call hooverb() |
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call check(update_nlist) |
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if (do_pot) then |
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call calc_forces(update_nlist,nmflag,pe = nose_status%pot_e) |
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else |
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call calc_forces(update_nlist,nmflag) |
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endif |
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call hoovera() |
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call evolve_time(step,nose_status,do_pot,not_done) |
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#ifdef MPI |
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call mpi_barrier(mpi_comm_world,mpi_err) |
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#endif |
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end do dynamics |
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end subroutine nose_hoover_dynamics |
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subroutine hoovera() |
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use velocity, ONLY : remove_cm_momentum,remove_angular_momentum |
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! ** CONSTANT-TEMPERATURE MOLECULAR DYNAMICS USING CONSTRAINT. ** |
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! ** ** |
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! ** REFERENCES: ** |
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! ** ** |
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! ** HOOVER, LADD, AND MORAN, PHYS REV LETT 48, 1818, 1982. ** |
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! ** EVANS, J CHEM PHYS 78, 3297, 1983. ** |
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! ** BROWN AND CLARKE, MOL PHYS, 51, 1243, 1984. ** |
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! ** ** |
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! ** ROUTINES SUPPLIED: ** |
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! ** ** |
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! ** SUBROUTINE HOOVERA ( ) ** |
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! ** FIRST PART OF MOVE WITH VELOCITY CONSTRAINTS APPLIED. ** |
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! ** SUBROUTINE HOOVERB ( DT ) ** |
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! ** SECOND PART OF MOVE. ** |
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integer :: i, dim |
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real( kind = DP) :: ke, v2, instatemp, chi |
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real( kind = DP) :: kebar |
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real( kind = DP ), dimension(ndim) :: v_dim_i |
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real(kind=DP) :: ke_local |
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! units for time are femtosec (10^-15 sec) |
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! units for distance are angstroms (10^-10 m) |
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! units for velocity are angstroms femtosec^-1 |
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! units for mass are a.m.u. (1.661 * 10^-27 kg) |
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! units for force are kcal mol^-1 angstrom^-1 |
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! |
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! converter will put the final terms into angstroms. |
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! or angstrom/femtosecond. |
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! converter = 1.0d0/2.390664d3 |
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! first calculate the temperature using the unconstrained velocities: |
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ke = 0.0E0_DP |
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ke_local = 0.0E0_DP |
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DO i = 1, nlocal |
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do dim = 1, ndim |
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v_dim_i(dim) = v(dim,i) + (dt2*f(dim,i)/mass(i))*KCALMOL_TO_AMUA2FS2 |
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ke_local = ke_local + mass(i)* & |
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(v_dim_i(dim)*v_dim_i(dim)) |
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enddo |
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enddo |
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#ifdef MPI |
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call mpi_allreduce(ke_local,ke,1,mpi_double_precision, & |
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mpi_sum,mpi_comm_world,mpi_err) |
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#else |
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ke = ke_local |
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#endif |
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ke = ke * AMUA2FS2_TO_KCALMOL |
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kebar = kcal_to_kj*1000.0e0_DP*ke / real(3*(natoms - 1),DP) / NAVOGADRO |
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instatemp = kebar/k_boltz |
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!write(*,*) 'before, insta = ', instatemp |
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chi = sqrt(target_temp / instatemp) |
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! ** CALCULATE THE CONSTRAINED VELOCITIES AT TIME T+DT/2 ** |
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do i = 1, nlocal |
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do dim = 1, ndim |
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v(dim,i) = v(dim,i) * (2.0E0_DP * chi - 1.0E0_DP) + & |
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chi*dt*(f(dim,i)/mass(i))*KCALMOL_TO_AMUA2FS2 |
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enddo |
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enddo |
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if (sim_type == "cluster") then |
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call remove_cm_momentum() |
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call remove_angular_momentum() |
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endif |
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end subroutine hoovera |
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subroutine hooverb( ) |
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! ******************************************************************* |
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! ** SECOND PART OF THE CONSTANT TEMPERATURE ALGORITHM ** |
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! ** ** |
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! ** THIS ADVANCES THE POSITIONS FROM T TO T + DT. ** |
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! ******************************************************************* |
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integer i, dim |
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! units for time are femtosec (10^-15 sec) |
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! units for distance are angstroms (10^-10 m) |
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! units for velocity are angstroms femtosec^-1 |
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! units for mass are a.m.u. (1.661 * 10^-27 kg) |
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! units for force are kcal mol^-1 angstrom^-1 |
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do i = 1, nlocal |
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do dim = 1, ndim |
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q(dim,i) = q(dim,i) + dt * v(dim,i) |
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enddo |
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enddo |
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end subroutine hooverb |
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end module dynamics_nose_hoover |
