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module dynamics_velocity_verlet |
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use simulation |
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use definitions, ONLY : DP, NDIM |
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use constants |
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use parameter |
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use force_module, ONLY : calc_forces |
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use velocity, ONLY : scale_velocities |
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use force_utilities, ONLY : check |
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use dynamics_utilities, ONLY : evolve_time, init_dynamics_loop, sim_status, & |
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DT2,DTSQRT,DTSQ2, init_status |
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#ifdef MPI |
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use mpi_module |
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#endif |
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implicit none |
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public :: velocity_verlet_dynamics |
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private :: movea, moveb |
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type (sim_status) :: verlet_status |
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contains |
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subroutine velocity_verlet_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(verlet_status) |
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call init_dynamics_loop(verlet_status) |
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! Start the main simulation loop. |
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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(verlet_status%temp) |
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if (dabs(verlet_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 movea() |
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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 = verlet_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 moveb() |
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call evolve_time(step,verlet_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 velocity_verlet_dynamics |
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|
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! ******************************************************************* |
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! ** FICHE F.4 ** |
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! ** TWO ROUTINES THAT TOGETHER IMPLEMENT VELOCITY VERLET METHOD. ** |
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! ** ** |
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! ** REFERENCE: ** |
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! ** ** |
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! ** SWOPE ET AL., J. CHEM. PHYS. 76, 637, 1982. ** |
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! ** ** |
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! ** ROUTINES SUPPLIED: ** |
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! ** ** |
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! ** SUBROUTINE MOVEA ( DT, M ) ** |
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! ** MOVES POSITIONS AND PARTIALLY UPDATES VELOCITIES. ** |
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! ** SUBROUTINE MOVEB ( DT, M, K ) ** |
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! ** COMPLETES VELOCITY MOVE AND CALCULATES KINETIC ENERGY. ** |
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! ** ** |
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! ** PRINCIPAL VARIABLES: ** |
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! ** ** |
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! ** INTEGER N NUMBER OF MOLECULES ** |
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! ** REAL DT TIMESTEP ** |
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! ** REAL M ATOMIC MASS ** |
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! ** REAL K KINETIC ENERGY ** |
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! ** REAL RX(N),RY(N),RZ(N) POSITIONS ** |
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! ** REAL VX(N),VY(N),VZ(N) VELOCITIES ** |
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! ** REAL FX(N),FY(N),FZ(N) FORCES ** |
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! ** ** |
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! ** USAGE: ** |
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! ** ** |
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! ** AT THE START OF A TIMESTEP, MOVEA IS CALLED TO ADVANCE THE ** |
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! ** POSITIONS AND 'HALF-ADVANCE' THE VELOCITIES. THEN THE FORCE ** |
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! ** ROUTINE IS CALLED, AND THIS IS FOLLOWED BY MOVEB WHICH ** |
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! ** COMPLETES THE ADVANCEMENT OF VELOCITIES. ** |
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! ******************************************************************* |
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subroutine movea( ) |
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! ******************************************************************* |
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! ** FIRST PART OF VELOCITY VERLET ALGORITHM ** |
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! ** ** |
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! ** USAGE: ** |
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! ** ** |
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! ** THE FIRST PART OF THE ALGORITHM IS A TAYLOR SERIES WHICH ** |
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! ** ADVANCES POSITIONS FROM T TO T + DT AND VELOCITIES FROM ** |
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! ** T TO T + DT/2. AFTER THIS, THE FORCE ROUTINE IS CALLED. ** |
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! ******************************************************************* |
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integer :: i, dim |
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! |
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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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! ******************************************************************* |
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do i = 1,nlocal |
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do dim = 1, 3 |
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q(dim,i) = q(dim,i) + dt*v(dim,i) + (dtsq2*f(dim,i)/mass(i))*KCALMOL_TO_AMUA2FS2 |
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v(dim,i) = v(dim,i) + (dt2*f(dim,i)/mass(i))*KCALMOL_TO_AMUA2FS2 |
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end do |
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end do |
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end subroutine movea |
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subroutine moveb() |
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#ifdef MPI |
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use mpi_module |
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#endif |
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! ******************************************************************* |
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! ** SECOND PART OF VELOCITY VERLET ALGORITHM ** |
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! ** ** |
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! ** USAGE: ** |
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! ** ** |
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! ** THE SECOND PART OF THE ALGORITHM ADVANCES VELOCITIES FROM ** |
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! ** T + DT/2 TO T + DT. THIS ASSUMES THAT FORCES HAVE BEEN ** |
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! ** COMPUTED IN THE FORCE ROUTINE AND STORED IN FX, FY, FZ. ** |
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! ******************************************************************* |
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integer :: i, dim |
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! |
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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 kcal/mol |
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! or angstrom/femtosecond. |
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! converter = 1.0d0/2.390664d3 |
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! ******************************************************************* |
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do i = 1, nlocal |
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do dim = 1, 3 |
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v(dim,i) = v(dim,i) + (dt2*f(dim,i)/mass(i))*KCALMOL_TO_AMUA2FS2 |
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end do |
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end do |
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end subroutine moveb |
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!! modified to be used in a mpi simulation..... |
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end module dynamics_velocity_verlet |
