AMBER Archive (2009)

Subject: [AMBER] R.E.D. too small charges

From: Andrei Neamtu (neamtuandrei_at_gmail.com)
Date: Fri Nov 13 2009 - 02:57:04 CST

Hello,

I am trying to reproduce the charges of alpha-D-glucopyranose form:

Restrained electrostatic potential atomic partial charges for
condensed-phase simulations of carbohydrates
R. J. Woods and R. Chappelle
Journal of Molecular Structure: THEOCHEM
Volume 527, Issues 1-3, 4 August 2000, Pages 149-156

 using GAMESS-US and R.E.D. III.3

The problem I face is that I obtain too small charges for all the
heavy atoms in the molecule compared to the ones in the paper above.
I use the same approach as described in the paper:
          Charges I obtain Charges from Woods & Chappelle
  1 O1 -0.3074 **** -0.6887
  2 HO1 0.3037 **** 0.4772
  3 C1 -0.0319 **** 0.2552
  4 H1 0.1292 **** 0.1186
  5 C2 -0.0307 **** 0.2474
  6 H2 0.1281 **** 0.0978
  7 O2 -0.3825 **** -0.6640
  8 H2O 0.2603 **** 0.4281
  9 C3 -0.0266 **** 0.1484
 10 H3 0.1228 **** 0.1188
 11 O3 -0.3477 **** -0.6732
 12 H3O 0.2783 **** 0.4357
 13 C4 -0.0385 **** 0.0492
 14 H4 0.1298 **** 0.0754
 15 O4 -0.3830 **** -0.6607
 16 H4O 0.2614 **** 0.0754
 17 C5 -0.0329 **** 0.2047
 18 H5 0.0963 **** 0.1295
 19 O5 -0.1371 **** -0.4966
 20 C6 -0.0139 **** 0.2543
 21 H61 0.0984 **** -0.0080
 22 H62 0.0984 **** 0.0003
 23 O6 -0.5796 **** -0.6805
 24 H6O 0.4052 **** 0.4266

I understand that charges depend on conformation but the differences
are simply too big.
This problem also appear on all monosaccarides that I had tried to
compute the charges for and even for smaller molecules.
I am fairly new to charge derivation and I tried to solve this for two
weeks without any success. It is obvious that I do a mistake
somewhere.
GAMESS installation is working properly as it passed all the tests.
Also the structures minimized within REDIII charge derivation process
are OK as tested with another QM software at the same level of
description.
I think the things go wrong somehere in the RESP procedure but I can't
seee where.
I am using RESP-C2 charge derivation method with qwt= 0.0100 and CHELPG

Here is the GAMESS input header:

! Single point to get MEP - Input generated by R.E.D.-III
!
 $CONTRL ICHARG=0 MULT=1 RUNTYP=ENERGY MOLPLT=.T.
         MPLEVL=0 UNITS=ANGS MAXIT=200 EXETYP=RUN
         SCFTYP=RHF
         COORD=UNIQUE $END
 $SCF DIRSCF=.T. CONV=1.0E-06 $END
 $SYSTEM TIMLIM=5000 MWORDS=32 MEMDDI=0 $END
 $BASIS GBASIS=N31 NGAUSS=6 NDFUNC=1 $END
 $GUESS GUESS=HUCKEL $END
! CHELPG/CONNOLLY CHARGES
 $ELPOT IEPOT=1 WHERE=PDC OUTPUT=BOTH $END
 $PDC PTSEL=CHELPG CONSTR=NONE $END
 $DATA

and,

Here is the RESP input header:

 RESP-C2 project. RESP input generated by R.E.D.
 &cntrl
  ioutopt=1, iqopt=1, nmol=1, ihfree=1, irstrnt=1, qwt= 0.0100
 &end

Any help would be greatly appreciated,
Andrei

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