[Pw_forum] md calculation and constraints in 4.3.2

[Jean-Roch Huntzinger]

Dear all,

Are 'md' calculations compatible with constraints in 4.3.2 ?

The following error occurs :
"constraints only with damped dynamics and fixed cell"
(in acetylene.out attached)
with qe-4.3.2, following the nice hands-on tutorial, relaxation part, at
http://www.fisica.uniud.it/~giannozz/QE-Tutorial/
using the modified input acetylene-SHAKE_mod.in (attached)
(modified because the format seems to have changed a little since 
the writing of the tutorial)


But the INPUT_PW.html says that
CONSTRAINTS is an
"Optional card, used for constrained dynamics or constrained optimisations 
(only if ion_dynamics='damp' or 'verlet', variable-cell excepted)"
This is also supported by
CASE ( calculation = 'md' )
    'verlet' : (default)   use Verlet algorithm to integrate
                           Newton's equation. For constrained
                           dynamics, see CONSTRAINTS card

So constraints should work with md and verlet ?

but in PW/input.f90 there is, line 1436 :
  IF ( lconstrain ) THEN
     IF ( .NOT. ldamped .OR. lmovecell ) CALL errore( 'iosys', &
              'constraints only with damped dynamics and fixed cell', 1 )

which seems to forbid constraints with verlet ?
(This has been introduced in Revision 7099 )

Note: changing 'verlet' to 'langevin' yields the same error, 
And actually ldamped is not defined for 'md' calculations 
(ibid, lines 372-393)



Should 'md' calculations really work with constraints or not ?
Or am I missing anything ?


Best regards,
Jean-Roch Huntzinger

-- 
L2C/SMC UMR 5221 - Université Montpellier 2, CNRS
case courrier 074
34095 Montpellier cedex 5
tel: 04 67 14 41 38
fax: 04 67 14 37 60
-------------- next part --------------
 &CONTROL
                 calculation = 'md' ,
                restart_mode = 'restart' ,
                  pseudo_dir = './' ,
                       nstep = 50 ,
                          dt = 10.D0 ,
 /
 &SYSTEM
                       ibrav = 1,
                   celldm(1) = 10.D0,
                         nat = 4,
                        ntyp = 2,
                     ecutwfc = 24.0D0 ,
                     ecutrho = 144.0D0 ,
                       nosym = .true. ,
                 occupations = 'smearing' ,
                     degauss = 0.01D0 ,
                    smearing = 'gaussian' ,
 /
 &ELECTRONS
                    conv_thr = 1.D-7 ,
                 mixing_beta = 0.5D0 ,
 /
 &IONS
                ion_dynamics = 'verlet' ,
           pot_extrapolation = 'second_order' ,
           wfc_extrapolation = 'second_order' ,
 /
ATOMIC_SPECIES
    H    1.00000  H.US_PBE.RRKJ3.UPF 
    C   12.00000  C.US_PBE.RRKJ3.UPF 
ATOMIC_POSITIONS bohr 
    C      0.000000000    0.000000000    0.000000000    0  0  0 
    C      2.100000000    0.000000000    0.000000000    
    H     -1.600000000    0.400000000    0.000000000    
    H      3.600000000   -0.400000000    0.000000000    
K_POINTS gamma 
CONSTRAINTS
  3 1e-8 
  'planar_angle'       1 2 4
  'distance'      1 3 
  'distance'      2 4 

-------------- next part --------------

     Program PWSCF v.4.3.2      starts on  8Jan2012 at  2:15:46 

     This program is part of the open-source Quantum ESPRESSO suite
     for quantum simulation of materials; please cite
         "P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
          URL http://www.quantum-espresso.org", 
     in publications or presentations arising from this work. More details at
     http://www.quantum-espresso.org/wiki/index.php/Citing_Quantum-ESPRESSO

     Current dimensions of program PWSCF are:
     Max number of different atomic species (ntypx) = 10
     Max number of k-points (npk) =  40000
     Max angular momentum in pseudopotentials (lmaxx) =  3
     Waiting for input...
     Reading input from stdin
     Reading   3 constraints; tolerance:    0.000000
         1) planar angle between atoms:   1  2  4
         2) distance between atoms:   1  3
         3) distance between atoms:   2  4
               file H.US_PBE.RRKJ3.UPF: wavefunction(s)  1S renormalized
               file C.US_PBE.RRKJ3.UPF: wavefunction(s)  2S 2P renormalized

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     from iosys : error #         1
     constraints only with damped dynamics and fixed cell
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

     stopping ...