pair_style coul/wolf 0.2 9.0 pair_coeff * *+
pair_style coul/streitz 12.0 ewald +pair_style coul/streitz 12.0 wolf 0.30 +pair_coeff * * AlO.streitz Al O +
pair_style tip4p/cut 1 2 7 8 0.15 12.0 pair_coeff * *@@ -110,6 +117,8 @@ the 2 atoms, and epsilon is the dielectric constant which can be set by the dielectric command. The cutoff Rc truncates the interaction distance. +
Style coul/debye adds an additional exp() damping factor to the Coulombic term, given by
@@ -118,6 +127,8 @@ Coulombic term, given bywhere kappa is the Debye length. This potential is another way to mimic the screening effect of a polar solvent.
+Style coul/dsf computes Coulombic interactions via the damped shifted force model described in Fennell, given by:
@@ -129,6 +140,8 @@ Wolf model (described below) to provide consistent forces and energies (the Wolf potential is not differentiable at the cutoff) and smooth decay to zero. +Style coul/wolf computes Coulombic interactions via the Wolf summation method, described in Wolf, given by:
@@ -147,6 +160,46 @@ forces calcluated by the Wolf summation method approach those of the Ewald sum. So it is a means of getting effective long-range interactions with a short-range potential. +Style coul/streitz is the Coulomb pair interaction defined as part +of the Streitz-Mintmire potential, as described in this +paper, in which charge distribution about an atom is modeled +as a Slater 1s orbital. More details can be found in the referenced +paper. To fully reproduce the published Streitz-Mintmire potential, +which is a variable charge potential, style coul/streitz must be +used with pair_style eam/alloy via the pair_style +hybrid/overlay command and charge equilibration must +be performed via the fix qeq/slater command. For +example: +
+pair_style hybrid/overlay coul/streitz 12.0 wolf 0.31 eam/alloy +pair_coeff * * coul/streitz AlO.streitz Al O +pair_coeff * * eam/alloy AlO.eam.alloy Al O +fix 1 all qeq/slater 1 12.0 1.0e-6 100 coul/streitz ++
The keyword wolf after the 12.0 cutoff denotes computing Coulombic +interactions via Wolf summation. An additional damping parameter is +required for the Wolf summation, as described for the coul/wolf +potential above. Alternatively, Coulombic interactions can be +computed via an Ewald summation. For example: +
+pair_style hybrid/overlay coul/streitz 12.0 ewald eam/alloy +kspace_style ewald 1e-6 ++
Keyword ewald does not need a damping parameter, but a +kspace_style must be defined. The Ewald summation +option was the method used in Streitz and Mintmire's original paper, +but a Wolf summation offers a speed-up in some cases. +
+For the fix qeq/slater command, the qfile can be a filename that +contains QEq parameters as discussed on the fix qeq +command doc page. Alternatively qfile can be replaced by +"coul/streitz", in which case the fix will extract QEq parameters from +the coul/streitz pair style itself. +
+Styles coul/long and coul/msm compute the same Coulombic interactions as style coul/cut except that an additional damping factor is applied so it can be used in conjunction with the @@ -285,4 +338,9 @@ Phys, 110, 8254 (1999).
(Fennell) C. J. Fennell, J. D. Gezelter, J Chem Phys, 124, 234104 (2006).
+ + +(Streitz) F. H. Streitz, J. W. Minimire, Phys Rev B 50, +11996-12003 (1994). +