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From: Monika Madhavi (monikamadhavi_at_gmail.com)
Date: Fri Sep 11 2015 - 00:48:51 CDT

Dear all,

I am trying to simulate a tip4p water box. Using the information on
toppar_water_ions_tip4p.str file given in toppar_36 force field parameters,
I wrote parameter and topology files as given below.

!parameters for tip4p water

ATOMS
MASS 1 HT 1.00800 ! TIPS3P WATER HYDROGEN
MASS 3 OT 15.99940 ! TIPS3P WATER OXYGEN
MASS 16 LP 0.00000 ! virtual particle for M-site/lone pairs

BONDS
HT HT 0.0 1.5139 ! from TIPS3P geometry (for SHAKE w/PARAM)
HT OT 450.0 0.9572 ! from TIPS3P geometry
OT LP 0.0 0.15 ! from TIP4P geometry

ANGLES
HT OT HT 55.0 104.52 ! FROM TIPS3P GEOMETRY

DIHEDRALS

IMPROPER

NONBONDED nbxmod 5 atom cdiel shift vatom vdistance vswitch -
cutnb 14.0 ctofnb 12.0 ctonnb 10.0 eps 1.0 e14fac 1.0 wmin 1.5

!TIP4P
HT 0.0 -0.0 0.0
OT 0.0 -0.155 1.7699
LP 0.0 -0.00 0.0

END

!topology for tip4p water

MASS 1 HT 1.00800 H ! TIPS3P WATER HYDROGEN
MASS 3 OT 15.99940 O ! TIPS3P WATER OXYGEN, TIP4
MASS 16 LP 0.00000 H ! virtual particle for M-site/lone pairs

default first none last none

RESI TP4P 0.000 ! tip4p water model, generate using noangle
nodihedral
GROUP
ATOM OW OT 0.0
ATOM OM LP -1.04
ATOM HW1 HT 0.52
ATOM HW2 HT 0.52
BOND OW HW1 OW HW2 HW1 HW2 ! the last bond is needed for shake
BOND OW OM
ANGLE HW1 OW HW2 ! required
ACCEPTOR OW
!DONOR H1 OH2
!DONOR H2 OH2
LONEPAIR bisector OM OW HW1 HW2 distance 0.15 angle 0.0 dihe 0.0
IC HW1 OM *OW HW2 0.9572 52.26 180.00 52.26 0.9572
IC HW2 HW1 OW OM 0.0000 0.00 0.00 52.26 0.15
PATCHING FIRS NONE LAST NONE

END

When I tried to build the psf file using psfgen, it gives me the following
error after reading the topology.

ERROR! FAILED TO RECOGNIZE LONEPAIR

What could be the reason for this?

Thank you.

Regards,
Monika 

-- 
W.A.Monika Madhavi
Lecturer (Probation),
Department of Physics,
University of Colombo.