I have posted the question using the <span class="gmail_quote"><<a href="mailto:gmx-users@gromacs.org">gmx-users@gromacs.org</a>>, but no reply. Therefore, I submit it here. </span><br><br>---------- Forwarded message ----------
<br><span class="gmail_quote">From: <b class="gmail_sendername">Qiao Baofu</b> <<a href="mailto:qiaobf@gmail.com">qiaobf@gmail.com</a>><br>Date: 2006-12-9 ÏÂÎç7:50<br>Subject: Re: [gmx-users] Re: fudgeQQ (again ...) and fudgeLJ
<br>To: Discussion list for GROMACS users <<a href="mailto:gmx-users@gromacs.org">gmx-users@gromacs.org</a>><br><br></span>Hi,<br>
<br>
I have just tested the fudgeQQ and fudgeLJ, and found one problem:<br>
I use the ffoplsaa force field, and add the atoms I used.(in the
ffolpsaanb.itp file, there is no [pairtype] section, and I only add the
atom informations:<br>
; name bond_type mass
charge
ptype
sigma epsilon<br>
opls_966 CT
6 12.01100
0 A 3.40000e-01
4.5770e-01) <br>
I write my .itp file by hand, in which in the [ pairs] section, I
write the pairs and the function, but don't give the values of C6 and
C12, that is,<br>
[ pairs ]<br>
; ai aj fu c6 c12<br>
1 5 1 <br>
1 6 1 <br>
...........<br>
<br>
In the ffoplsaa.itp, I used <br>
; nbfunc comb-rule gen-pairs fudgeLJ fudgeQQ<br>
1
2
yes 0.5
0.8333<br>
<br>
I used different values of fudgeLJ and fudgeQQ in the 4 tests, see the following <br>
fudgeLJ
fudgeQQ result (from .log file):
LJ-14
Coulomb-14<br>
1. 0.5
0.5
1.48e+02
-8.896e+03<br>
2 1
1
1.96e+02 -1.793e+04<br>
3. 0.25
0.25
9.58e+01
-4.43e+03
<br>
4. 0.5
0.8333
1.96e+02
-1.498e+04 <br>
<br>
The problem is that the LJ-14 doesn't change with the scaling factor of fudgeLJ. Why? <br>
<br>
Does it mean that I must give the C6 and C12 in the .itp file? If yes,
should the C6 and C12 scaled by the scaling factor (0.5) and "gen-pairs
= no; fudgeLJ=1" ?<br>
<br>
Another question is that in the .log file, what is the "Disper.
corr."? What is the difference between it and the 1-4 interacion?<br>
<br clear="all"><br>-- <br>Sincerely yours,<br>**********************************************<br>Baofu Qiao, PhD<br>Frankfurt Institute for Advanced Studies<br>Max-von-Laue-Str. 1<br>60438 Frankfurt am Main, Germany <br>
TEL:+49-69-7984-7529<br>**********************************************