[QE-users] Problem with constraint optimisation routine

[Sourav Mondal]

Dear QE experts,
    I am trying to use constraint optimization technique implemented in QE,
but I facing an error.  I want to use this technique for my system to fix
more than one bond distances. For simplicity, I tried this technique on CO2
molecule where I constraint one bond initially and  It works finely for one
bond, but when I tried to fix more than one bonds, it fails to work. I
found it simply does relaxation without constraining the bond distances if
I try to constraint more than one bond. Is there any solution available for
this?  I am attaching my input file with this mail.

&control
        calculation='relax'
        restart_mode='from_scratch',
        prefix='CO2',
        pseudo_dir= './pseudo'
        outdir='./tmp_CO2'
        tstress= .true.
/
 &system
    ibrav = 1,
    celldm(1)= 11.000000,
    nat = 3, ntyp = 2,
    ecutwfc = 40, ecutrho = 320,
    occupations='smearing', smearing='mv', degauss=0.001,
   nosym= .true.
/
 &electrons
    diagonalization = 'david', mixing_mode = 'local-TF',
    mixing_beta = 0.1, conv_thr = 1.D-6
    startingwfc = 'random'
/
 &ions
   ion_dynamics = 'damp'

/
ATOMIC_SPECIES
C   1.000    C.pz-n-rrkjus_psl.0.1.UPF
O   1.008    O.pz-n-rrkjus_psl.0.1.UPF
K_POINTS {gamma}
ATOMIC_POSITIONS {angstrom}
C  0.0000000   0.0000000   0.0000000
O  0.0000000   0.0000000   1.5140760
O  0.0000000   0.0000000  -1.5140760

CONSTRAINTS
2
'distance', 1, 2, 3.1
'distance', 1, 3, 2.8


Thank you very much.

Regards
--------------------------------------------
Sourav Mondal
PhD Student
JNCASR , Bangalore
Pin- 560064
India
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