Hello,
I have been getting some weird stress values in MD calculations using cp.x
from QE 7.2 with ultrasoft pseudopotentials and after some rummaging I have
found a couple of bugs:
i) The dbec array gets inadvertantly altered through the call to cg_sub.f90
where is is assigned a different size "real(dp) :: dbec(nkb, nbspx, 3, 3)" than
initially allocated in mainvar.f90 "ALLOCATE( dbec( nhsa, 2*nrcx, 3, 3 ),
STAT=ierr )". The upshot of this is that the values of dbec get jumbled and the
resulting stress tensor is messed up (and physically nonsensical). Also, since
dbec is not zeroed and the initially allocated size does not seem to correspond
to the used size, this also has the effect of introducing random values into
the stress tensor, although zeroing dbec after the allocation in mainvar.f90
fixes this.
ii) In fromscra.f90 the constraints contribution to the stress is calculated
"if ( tstress ) CALL nlfh( stress, bec_bgrp, dbec, lambda, idesc )" before the
dbec array has been calculated "if ( tstress ) CALL caldbec_bgrp( eigr,
cm_bgrp, dbec, idesc )".
Kind regards,
Jeremy
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