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From: jim caldwell <caldwell_at_heimdal.compchem.ucsf.edu>

Date: Tue 29 Aug 2000 12:57:57 -0700 (PDT)

The relationships are found in Fox & Kollman, JPC B. 102, 8070-8079

eps(ij) = sqrt(eps(i)*eps(j))

Rij = Ri + Rj

Aij = eps(ij) * (Rij)**12

Bij = 2 * eps(ij) * (Rij)**6

jim

On Tue, 29 Aug 2000 hsk_at_nemo.physics.ncsu.edu wrote:

*> Hi !
*

*>
*

*> I cannot find any clear explanation on how parameters for the van der
*

*> Waals (vdW) interaction of a pair of unlike species are related to those
*

*> read from the parameter file. For example, how do you calculate the
*

*> (6-12) interaction energy between a pair of C and N atoms ? There are
*

*> several issues here.
*

*>
*

*> (1) Is vdW interactiond efined by
*

*>
*

*> V(r) = 4*epsilon*[ (sigma/r)**12 - (sigma/r)**6] ?
*

*>
*

*> Here, 'epsilon' and 'sigma' are potential depth and the characteristic
*

*> distance for the pair interaction.a If this not correct, where can I find
*

*> the correct one ?
*

*>
*

*> (2) Is 'epsilon' defined by the following relation ?
*

*>
*

*> epsilon = (epsilon_1 * epsilon_2)**(1/2),
*

*>
*

*> where 'epsilon_1' and 'epsilon_2' are "well-depth" in the parameter file
*

*> (with the option "KINDNB=RE"). If this is not correct, the where can I
*

*> find the correct relation ?
*

*>
*

*> (3) Is 'sigma' defined by the following relation ?
*

*>
*

*> sigma = (sigma_1 + sigma_2)/2
*

*>
*

*> where 'sigma_1' and 'sigma_2' are so-called vdw radii which are alos from
*

*> the parameter file ?
*

*>
*

*> I tried to find the answers to these questions, and could not.
*

*>
*

*> I hope that I could get answeres soon.
*

*>
*

*> Sincerely,
*

*>
*

*> Hong Seok Kang
*

*>
*

*> Currently, Visiting Profesor to
*

*> Department of Physics
*

*> North Carolina State Universaity
*

*> NC 27607
*

*> (919)515-9123
*

*>
*

*> Aug, 29, 2000
*

*>
*

*>
*

----------------------------------------------------------------------------

James W. Caldwell (voice) 415-476-8603

Department of Pharmaceutical Chemistry (fax) 415-502-1411

Mail Stop 0446 (email) caldwell_at_heimdal.ucsf.edu

513 Parnassus Avenue

University of California

San Francisco, CA 94143-0446

----------------------------------------------------------------------------

Received on Tue Aug 29 2000 - 12:57:57 PDT

Date: Tue 29 Aug 2000 12:57:57 -0700 (PDT)

The relationships are found in Fox & Kollman, JPC B. 102, 8070-8079

eps(ij) = sqrt(eps(i)*eps(j))

Rij = Ri + Rj

Aij = eps(ij) * (Rij)**12

Bij = 2 * eps(ij) * (Rij)**6

jim

On Tue, 29 Aug 2000 hsk_at_nemo.physics.ncsu.edu wrote:

----------------------------------------------------------------------------

James W. Caldwell (voice) 415-476-8603

Department of Pharmaceutical Chemistry (fax) 415-502-1411

Mail Stop 0446 (email) caldwell_at_heimdal.ucsf.edu

513 Parnassus Avenue

University of California

San Francisco, CA 94143-0446

----------------------------------------------------------------------------

Received on Tue Aug 29 2000 - 12:57:57 PDT

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