AMBER Archive (2003)

Subject: SPC/E model -LJ parameters

From: Ioana Cozmuta (ioana_at_nas.nasa.gov)
Date: Sun May 04 2003 - 16:55:53 CDT

Hi,

A small correction.
If I use rdparm printLennardJones parameters I get that
A = 629362.17
C = 625.27
and I assume that these units are (kcal/mol)^(1/12 or 1/6) *A as the van
der waals energy is in kcal/mol.
Using these parameters the vdw energy corresponding to r = 2.7 A is a
positive number.

The printTypes command gives
Type r* eps
OW 1.7767 0.1553

The vdw energy here corresponding to r = 2.7A is a negative number.

I thought that A = eps*(r*)^12 =153.65 and
C = 2*eps *(r*)^6 = 9.77

but these are different than the values given by the printLennardJones
command in rdparm.

Can anyone plese help me to figure out what is the correct relation?

Thank you,
Ioana