Dear All,
I am trying to run a QM/MM MD calculation on an enzyme substrate system using AMBER 18 (ambertools19) after successful completion of MD production run. It runs completely fine for short time (2ps) but for 20ps it start giving this error:
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 89; vmax = 34.2488
The same restart file runs with PM3 for 20ps but for DFTB and DFTB2 it gives convergence error.I have look around mailing list and also tried to used SCF iterationflag (itrmax) but no luck. Please suggest. Thanks in advance. Input file:20 ps QM/MM MD production&cntrl imin=0, irest=1, ntx=5, nstlim=20000, dt=0.001, ntpr=100, ntwx=500, ioutfm=1, ntc=2, ntf=2, ntb=2, cut=10.0, ntp=1, pres0=1.0, taup=5.0, ntt=3, tempi=300.0, temp0=300.0, gamma_ln=5, ig=-1, ifqnt=1, nmropt=1,/&qmmm qmmask='.3989-3991,2162-2167,688-715,720-723', qmcharge=-2, qm_theory='DFTB2', qmshake=0, qm_ewald=1, qm_pme=1, itrmax=1000,/&wt type='DUMPFREQ', istep1=1 /&wt type='END' /DISANG=rc0.8_3.5.RSTDUMPAVE=rc0.8_3.5_2ps.tra/Thanks,Sarah
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Received on Wed Oct 07 2020 - 10:30:03 PDT
