# Re: [AMBER] QM/MM Convergence questions

From: Busra Demir <bdemir09.gmail.com>
Date: Thu, 5 Mar 2020 14:41:27 +0300

Your SCF calculation didn't converge. This could be due to various reasons
and G09 doesn't specifically say it.
First, you should check the input parameters you choose such as charge and
multiplicity for the calculation.

If you are sure about them, there are several options but (to the best of
my knowledge) these are the first things you could try:
1. try increasing number of cycles (maxcycle=xxx) in G09 input route line.
2. change the convergence criteria for SCF calculation (use SCF=QC instead
of default SCF=Tight).
3. change convergence criteria scf_conv under &gau namelist.

You can find more options about SCF calculations from gaussian website:
https://gaussian.com/scf/

Busra Demir

PhD Student
Department of Materials Science and Nanotechnology Engineering
Bionanodesign Laboratory,
TOBB University of Economics and Technology
Ankara, 06560 TURKEY

On Thu, Mar 5, 2020 at 12:07 PM 辛志宏 <xzhfood.njau.edu.cn> wrote:

> Dear Amber,
>
> An error occur when I run a QM/MM with amber and gausssin09, I do not know
> how to solve the problems, any suggestion will be much appreciate, thank
> you for your help in advanced, the error information is as follows:
>
> The QM/MM input file:
>
> Initial min of our structure QMMM
> &cntrl
> imin = 1, maxcyc = 5000, ncyc=2000,
> ntb = 0,
> cut = 20.0, ntc=2, ntf=2,
> ntpr=1000,
> restraint_wt=2.0,
> ifqnt = 1
> &end
> &qmmm
>
> iqmatoms=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,715,716,717,718,719,720,721,722,723,724,725,757,758,759,760,761,762,763,764,765,766,767,768,769,770,771,772,773,774,775,776,777,778,2365,2366,2367,2368,2369,2370,2371,2372,2373,2374,2375,2376,2377,2378,2379,2382,8628,8629,8630,8679,8680,8681
> qmcharge = 0,
> spin = 2,
> qm_theory = 'EXTERN',
> qmshake=1,
> qm_ewald=1, qm_pme=1,
> diag_routine=0,
> writepdb=1
> qmcut = 20.0
> &end
> &gau
> method = 'B3LYP',
> basis = '6-31G*',
> mem = '6GB'
> &end
>
>
> Error form the gau_job.log file,
> .....................................
> RMSDP=1.93D-04 MaxDP=3.33D-02 DE= 1.64D-04 OVMax= 8.63D-02
>
> Cycle 128 Pass 1 IDiag 1:
> RMSU= 2.75D-05 CP: 1.00D+00 -5.05D-01 -8.69D-01 2.19D+00
> E= -2424.60356615312 Delta-E= 0.001037414186 Rises=F Damp=F
> DIIS: error= 8.55D-04 at cycle 125 NSaved= 20.
> NSaved=20 IEnMin= 5 EnMin= -2424.61776698937 IErMin=19 ErrMin=
> 4.94D-04
> ErrMax= 8.55D-04 0.00D+00 EMaxC= 1.00D-01 BMatC= 3.31D-04 BMatP= 1.14D-04
> IDIUse=3 WtCom= 9.97D-01 WtEn= 2.98D-03
> Rare condition: small coef for last iteration: 0.000D+00
> Coeff-Com: -0.702D-01-0.293D-01-0.544D-01-0.305D+00 0.621D+00-0.423D+00
> Coeff-Com: -0.423D-01 0.140D+00 0.716D-01 0.997D-01-0.177D+00-0.897D-01
> Coeff-Com: 0.104D+00-0.256D+00 0.537D+00-0.734D+00 0.809D-01 0.274D+00
> Coeff-Com: 0.127D+01-0.203D-01
> Coeff-En: 0.000D+00 0.000D+00 0.000D+00 0.000D+00 0.000D+00 0.000D+00
> Coeff-En: 0.000D+00 0.000D+00 0.000D+00 0.000D+00 0.000D+00 0.000D+00
> Coeff-En: 0.000D+00 0.000D+00 0.000D+00 0.000D+00 0.000D+00 0.000D+00
> Coeff-En: 0.000D+00 0.100D+01
> Coeff: -0.702D-01-0.293D-01-0.544D-01-0.305D+00 0.621D+00-0.423D+00
> Coeff: -0.423D-01 0.140D+00 0.716D-01 0.997D-01-0.177D+00-0.897D-01
> Coeff: 0.104D+00-0.256D+00 0.537D+00-0.734D+00 0.809D-01 0.274D+00
> Coeff: 0.127D+01-0.203D-01
> Gap= 0.009 Goal= None Shift= 0.000
> Gap= 0.010 Goal= None Shift= 0.000
> RMSDP=6.02D-05 MaxDP=1.08D-02 DE= 1.04D-03 OVMax= 2.84D-02
>
> >>>>>>>>>> Convergence criterion not met.
> SCF Done: E(UB3LYP) = -2424.60356615 A.U. after 129 cycles
> NFock=128 Conv=0.60D-04 -V/T= 2.2388
> <Sx>= 0.0000 <Sy>= 0.0000 <Sz>= 0.5000 <S**2>= 1.5874 S= 0.8555
> <L.S>= 0.000000000000E+00
> KE= 1.957254069352D+03 PE=-1.340126621204D+04 EE= 5.052337417625D+03
> Annihilation of the first spin contaminant:
> S**2 before annihilation 1.5874, after 1.2129
> Convergence failure -- run terminated.
> Error termination via Lnk1e in /home/xzhfood/gaussian/g09/l502.exe at Thu
> Mar 5 03:47:42 2020.
> Job cpu time: 0 days 5 hours 47 minutes 3.7 seconds.
> File lengths (MBytes): RWF= 465 Int= 0 D2E= 0 Chk= 12
> Scr= 1
>
> Tianyou Xin
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Received on Thu Mar 05 2020 - 04:00:02 PST
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