[Pw_forum] structure oscillating with vc-md
Stefano de Gironcoli
degironc at sissa.it
Fri Oct 28 05:52:41 CEST 2011
Dear Amin Torabi
you are performing a variable-cell MD simulation therefore the
enthalpy is not minimized by the Newton equations for atoms+cell are
integrated to give you the dynamics around the target pressure (P=0 in
your case).
to get the relaxation you should use calculation = "vc-relax" and
then choose the minimization strategy.
the default is bfgs but also damp dynamics is available.
check the relevant input variables: ion_dynamics and cell_dynamics.
best regards,
stefano
On 10/28/2011 02:49 AM, Amin Torabi wrote:
> Dear QE users,
>
> Will you please do me a favor and take a look at my input file, below.
> The total energy and force do not converge and keep oscillating...
> I have tried different dt (between 20-70) and wmass, and still not able to
> relax the structure
> Any comment on my the input_cards here (k-point,ecut,pp,conv...?)
>
> Many thanks
>
>
>
> &CONTROL
> calculation = 'vc-md'
> pseudo_dir = './'
> outdir = './'
> prefix = 'dt20'
> tstress = .true
> tprnfor = .true
> nstep = 100
> dt = 20
> /
> &SYSTEM
> ibrav = 12
> celldm(1) = 8.3147
> celldm(2) = 1.3
> celldm(3) = 1.4772
> celldm(4) = -0.260
> nat = 16
> ntyp = 2
> ecutwfc = 85
> ecutrho = 1100
> input_dft = 'pbesol'
> nosym = .true
> /
> &ELECTRONS
> conv_thr = 1.0D-9
> /
> &IONS
> pot_extrapolation='second-order'
> wfc_extrapolation='second-order'
> ion_temperature = 'rescaling'
> tempw = 300
> /
> &CELL
> press = 0
> cell_dynamics = 'w'
> wmass = 4.2
> /
> ATOMIC_SPECIES
> B 10.811 B.pbe-n-van.UPF
> H 1.00794 H.pbe-van_bm.UPF
> ATOMIC_POSITIONS crystal
> B 0.005259620 0.145596712 0.040564862
> H -0.199830030 0.176142715 0.150841828
> H 0.217291388 0.312290957 -0.013967013
> H 0.124960907 -0.022012847 0.122883862
> B -0.005259620 -0.145596712 -0.040564862
> H 0.199830030 -0.176142715 -0.150841828
> H -0.217291388 -0.312290957 0.013967013
> H -0.124960907 0.022012847 -0.122883862
> B 0.494739818 0.354404554 0.540568678
> H 0.699828966 0.323861788 0.650847745
> H 0.282707973 0.187708799 0.486039576
> H 0.375038882 0.522017144 0.622882523
> B 0.505260182 0.645595446 0.459431322
> H 0.300171034 0.676138212 0.349152255
> H 0.717292027 0.812291201 0.513960424
> H 0.624961118 0.477982856 0.377117477
> K_POINTS automatic
> 8 8 8 0 0 0
>
>
>
>
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