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1 : !!****m* ABINIT/m_pred_langevin_pimd
2 : !! NAME
3 : !! m_pred_langevin_pimd
4 : !!
5 : !! FUNCTION
6 : !! This module provides an interface to call PIMD Langevin dynamics algorithm,
7 : !! for conventional NVT molecular dynamics.
8 : !!
9 : !! COPYRIGHT
10 : !! Copyright (C) 2024-2026 ABINIT group (A. Blanchet)
11 : !! This file is distributed under the terms of the
12 : !! GNU General Public License, see ~abinit/COPYING
13 : !! or http://www.gnu.org/copyleft/gpl.txt .
14 : !!
15 : !! SOURCE
16 :
17 : #if defined HAVE_CONFIG_H
18 : #include "config.h"
19 : #endif
20 :
21 : #include "abi_common.h"
22 :
23 : module m_pred_langevin_pimd
24 :
25 : use defs_basis
26 : use m_abicore
27 : use m_abimover
28 : use m_abihist
29 : use m_pimd
30 : use m_pimd_langevin, only : pimd_langevin_nvt,pimd_langevin_npt
31 : use m_geometry, only : metric
32 :
33 : implicit none
34 : public :: pred_langevin_pimd
35 :
36 : contains
37 :
38 : !!***
39 : !!****f* ABINIT/pred_langevin_pimd
40 : !! NAME
41 : !! pred_langevin_pimd
42 : !!
43 : !! FUNCTION
44 : !! Ionmov predictors (16) Langevin dynamics algorithm using PIMD predictor
45 : !!
46 : !! IONMOV 16:
47 : !! Uses a Langevin dynamics algorithm :
48 : !! see Quigley,Probert, JCP 120, 11432 (2004) [[cite:Quigley2004]], part III
49 : !!
50 : !! INPUTS
51 : !! ab_mover <type(abimover)> : Datatype with all the information needed by the preditor
52 : !! itime : Index of the present iteration
53 : !! zDEBUG : if true print some debugging information
54 : !! pimd_param=datastructure that contains all the parameters necessary to Path-Integral MD
55 : !!
56 : !! OUTPUT
57 : !!
58 : !! SIDE EFFECTS
59 : !! hist <type(abihist)> : History of positions,forces acell, rprimd, stresses
60 : !!
61 : !! SOURCE
62 :
63 10 : subroutine pred_langevin_pimd(ab_mover,hist,itime,zDEBUG,pimd_param)
64 :
65 : ! Arguments -------------------------------
66 : ! Scalars
67 : type(abimover),intent(in) :: ab_mover
68 : type(abihist),intent(inout) :: hist
69 : type(pimd_type),intent(in) :: pimd_param
70 : integer,intent(in) :: itime
71 : logical,intent(in) :: zDEBUG
72 :
73 : ! Local variables -------------------------
74 : ! Scalars
75 : integer :: ihist_prev
76 : real(dp) :: ucvol
77 : real(dp) :: etotal
78 : ! Arrays
79 : real(dp) :: acell(3),rprimd(3,3),rprimd_next(3,3),rprimd_prev(3,3),gprimd(3,3)
80 20 : real(dp) :: gmet(3,3),rmet(3,3),strten(6),fcart(3,ab_mover%natom)
81 20 : real(dp) :: xred(3,ab_mover%natom),vel(3,ab_mover%natom),vel_cell(3,3),vel_cell_next(3,3)
82 20 : real(dp) :: pimd_etotal(1),pimd_stressin(3,3,1),pimd_xred(3,ab_mover%natom,1)
83 20 : real(dp) :: pimd_xred_next(3,ab_mover%natom,1),pimd_xred_prev(3,ab_mover%natom,1)
84 20 : real(dp) :: pimd_forces(3,ab_mover%natom,1),pimd_vel(3,ab_mover%natom,1)
85 20 : real(dp) :: pimd_vel_next(3,ab_mover%natom,1)
86 :
87 : ! *********************************************************************
88 : ! Initialize arrays
89 10 : ihist_prev=0
90 10 : ucvol=zero
91 10 : etotal=zero
92 10 : acell=zero
93 10 : rprimd=zero
94 10 : rprimd_next=zero
95 10 : rprimd_prev=zero
96 10 : gprimd=zero
97 10 : gmet=zero
98 10 : rmet=zero
99 10 : strten=zero
100 250 : fcart=zero
101 250 : xred=zero
102 250 : vel=zero
103 10 : vel_cell=zero
104 10 : vel_cell_next=zero
105 10 : pimd_etotal=zero
106 10 : pimd_stressin=zero
107 260 : pimd_xred=zero
108 260 : pimd_xred_next=zero
109 260 : pimd_xred_prev=zero
110 260 : pimd_forces=zero
111 260 : pimd_vel=zero
112 260 : pimd_vel_next=zero
113 : ! Get last positions
114 10 : call hist2var(acell,hist,ab_mover%natom,rprimd,xred,zDEBUG)
115 250 : fcart(:,:)=hist%fcart(:,:,hist%ihist)
116 70 : strten(:) =hist%strten(:,hist%ihist)
117 250 : vel(:,:) =hist%vel(:,:,hist%ihist)
118 130 : vel_cell =hist%vel_cell(:,:,hist%ihist)
119 10 : etotal =hist%etot(hist%ihist)
120 10 : call metric(gmet,gprimd,-1,rmet,rprimd,ucvol)
121 :
122 : ! Set PIMD corresponding variables
123 10 : pimd_etotal(1)=etotal
124 10 : pimd_stressin(1,1,1)=strten(1)
125 10 : pimd_stressin(2,2,1)=strten(2)
126 10 : pimd_stressin(3,3,1)=strten(3)
127 10 : pimd_stressin(3,2,1)=strten(4)
128 10 : pimd_stressin(3,1,1)=strten(5)
129 10 : pimd_stressin(2,1,1)=strten(6)
130 250 : pimd_xred(:,:,1)=xred(:,:)
131 : ! Get quantities from previous step
132 10 : if(itime==1) then
133 50 : pimd_xred_prev(:,:,1)=xred(:,:)
134 2 : rprimd_prev(:,:)=rprimd(:,:)
135 : else
136 8 : ihist_prev = abihist_findIndex(hist,-1)
137 200 : pimd_xred_prev(:,:,1)=hist%xred(:,:,ihist_prev)
138 104 : rprimd_prev(:,:)=hist%rprimd(:,:,ihist_prev)
139 : endif
140 250 : pimd_forces(:,:,1)=fcart(:,:)
141 250 : pimd_vel(:,:,1)=vel(:,:)
142 :
143 : ! Compute next values
144 10 : if(pimd_param%optcell==0) then
145 : call pimd_langevin_nvt(pimd_etotal,pimd_forces,itime,ab_mover%natom,pimd_param,&
146 5 : & 0,rprimd,pimd_stressin,1,pimd_vel,pimd_vel_next,ucvol,pimd_xred,pimd_xred_next,pimd_xred_prev)
147 5 : rprimd_next=rprimd ! We do not change primitive vectors
148 5 : vel_cell=zero ! Cell velocities are set to zero
149 5 : elseif(pimd_param%optcell==2) then
150 : call pimd_langevin_npt(pimd_etotal,pimd_forces,itime,ab_mover%natom,pimd_param,&
151 : & 0,rprimd,rprimd_next,rprimd_prev,pimd_stressin,1,pimd_vel,pimd_vel_next,vel_cell,&
152 : & vel_cell_next,ucvol,&
153 5 : & pimd_xred,pimd_xred_next,pimd_xred_prev)
154 : endif
155 :
156 : ! Update hist
157 10 : hist%ihist = abihist_findIndex(hist,+1)
158 10 : call var2hist(acell,hist,ab_mover%natom,rprimd_next,pimd_xred_next(:,:,1),zDEBUG)
159 250 : hist%vel(:,:,hist%ihist)=pimd_vel(:,:,1)
160 130 : hist%vel_cell(:,:,hist%ihist)=vel_cell(:,:)
161 10 : hist%time(hist%ihist)=real(itime,kind=dp)*ab_mover%dtion
162 :
163 10 : end subroutine pred_langevin_pimd
164 : !!***
165 :
166 : end module m_pred_langevin_pimd
167 : !!***
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