Hello,
I run QM/MM computation but the QM region does not converge at all, and Amber keeps throwing errors:
# # # # # # # # # # # # # #
QMMM SCC-DFTB: !!!! ============= WARNING ============= !!!!
QMMM SCC-DFTB: Convergence could not be achieved in this step.
QMMM SCC-DFTB: The calculation will continue, but energies and
QMMM SCC-DFTB: forces for this step will not be accurate.
vlimit exceeded for step 223; vmax = 49.1365
# # # # # # # # # # # # # #
Although the jobs do not crash, the energies have NaN values at some point.
The input is as follows:
# # # # # # # # # # # # # #
Equilibration
&cntrl
dt=0.001, ! time-step [fs] (1 fs) {1 fs = 0.001 ps}
nstlim=50000, ! steps (50.000 steps) {50 ps = 0.001 ps * 50.000 steps}
taup=1, ! pressure relaxation time (1 ps)
ntc=2, ! SHAKE for bonds involving hydrogen are constrained
cut=8.0, ! direct-space cut-off of 8A for non-bonded interaction with PME for long-range electrostatics
ifqnt=1, ! turn-on QMMM
/
&qmmm
qmmask='.2135-2140 | u/4009-4011 | u/702-705 | u/670-697',! atom masks
qm_theory='SCC-DFTB', ! used QM theory
qmcharge=-2, ! charge of QM region
/
# # # # # # # # # # # # # #
What can I do. Following the paper I shall do # 300 ps unrestrained SCC- DFTB/ff12SB MD [...] on the equilibrated [...] complexes in the NPT ensemble.#
Sincerely,
--
Maciej
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Received on Sun Feb 19 2023 - 09:00:02 PST
