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58
doc/pair_coul.html
View File

@ -41,6 +41,8 @@
</H3>
<H3>pair_style coul/msm/omp command
</H3>
<H3>pair_style coul/streitz command
</H3>
<H3>pair_style coul/wolf command
</H3>
<H3>pair_style coul/wolf/kk command
@ -63,6 +65,7 @@ pair_style coul/dsf alpha cutoff
pair_style coul/long cutoff
pair_style coul/long/gpu cutoff
pair_style coul/wolf alpha cutoff
pair_style coul/streitz cutoff keyword alpha
pair_style tip4p/cut otype htype btype atype qdist cutoff
pair_style tip4p/long otype htype btype atype qdist cutoff
</PRE>
@ -92,6 +95,10 @@ pair_coeff * *
<PRE>pair_style coul/wolf 0.2 9.0
pair_coeff * *
</PRE>
<PRE>pair_style coul/streitz 12.0 ewald
pair_style coul/streitz 12.0 wolf 0.30
pair_coeff * * AlO.streitz Al O
</PRE>
<PRE>pair_style tip4p/cut 1 2 7 8 0.15 12.0
pair_coeff * *
</PRE>
@ -110,6 +117,8 @@ the 2 atoms, and epsilon is the dielectric constant which can be set
by the <A HREF = "dielectric.html">dielectric</A> command. The cutoff Rc truncates
the interaction distance.
</P>
<HR>
<P>Style <I>coul/debye</I> adds an additional exp() damping factor to the
Coulombic term, given by
</P>
@ -118,6 +127,8 @@ Coulombic term, given by
<P>where kappa is the Debye length. This potential is another way to
mimic the screening effect of a polar solvent.
</P>
<HR>
<P>Style <I>coul/dsf</I> computes Coulombic interactions via the damped
shifted force model described in <A HREF = "#Fennell">Fennell</A>, given by:
</P>
@ -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.
</P>
<HR>
<P>Style <I>coul/wolf</I> computes Coulombic interactions via the Wolf
summation method, described in <A HREF = "#Wolf">Wolf</A>, given by:
</P>
@ -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.
</P>
<HR>
<P>Style <I>coul/streitz</I> is the Coulomb pair interaction defined as part
of the Streitz-Mintmire potential, as described in <A HREF = "#Streitz">this
paper</A>, in which charge distribution about an atom is modeled
as a Slater 1<I>s</I> 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 <I>coul/streitz</I> must be
used with <A HREF = "pair_eam.html">pair_style eam/alloy</A> via the <A HREF = "pair_hybrid.html">pair_style
hybrid/overlay</A> command and charge equilibration must
be performed via the <A HREF = "fix_qeq.html">fix qeq/slater</A> command. For
example:
</P>
<PRE>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
</PRE>
<P>The keyword <I>wolf</I> after the 12.0 <I>cutoff</I> 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:
</P>
<PRE>pair_style hybrid/overlay coul/streitz 12.0 ewald eam/alloy
kspace_style ewald 1e-6
</PRE>
<P>Keyword <I>ewald</I> does not need a damping parameter, but a
<A HREF = "kspace_style.html">kspace_style</A> 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.
</P>
<P>For the fix qeq/slater command, the <I>qfile</I> can be a filename that
contains QEq parameters as discussed on the <A HREF = "fix_qeq.html">fix qeq</A>
command doc page. Alternatively <I>qfile</I> can be replaced by
"coul/streitz", in which case the fix will extract QEq parameters from
the coul/streitz pair style itself.
</P>
<HR>
<P>Styles <I>coul/long</I> and <I>coul/msm</I> compute the same Coulombic
interactions as style <I>coul/cut</I> 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).
<P><B>(Fennell)</B> C. J. Fennell, J. D. Gezelter, J Chem Phys, 124,
234104 (2006).
</P>
<A NAME = "Streitz"></A>
<P><B>(Streitz)</B> F. H. Streitz, J. W. Minimire, Phys Rev B 50,
11996-12003 (1994).
</P>
</HTML>

56
doc/pair_coul.txt
View File

@ -22,6 +22,7 @@ pair_style coul/long/omp command :h3
pair_style coul/long/gpu command :h3
pair_style coul/msm command :h3
pair_style coul/msm/omp command :h3
pair_style coul/streitz command :h3
pair_style coul/wolf command :h3
pair_style coul/wolf/kk command :h3
pair_style coul/wolf/omp command :h3
@ -38,6 +39,7 @@ pair_style coul/dsf alpha cutoff
pair_style coul/long cutoff
pair_style coul/long/gpu cutoff
pair_style coul/wolf alpha cutoff
pair_style coul/streitz cutoff keyword alpha
pair_style tip4p/cut otype htype btype atype qdist cutoff
pair_style tip4p/long otype htype btype atype qdist cutoff :pre
@ -67,6 +69,10 @@ pair_coeff * * :pre
pair_style coul/wolf 0.2 9.0
pair_coeff * * :pre
pair_style coul/streitz 12.0 ewald
pair_style coul/streitz 12.0 wolf 0.30
pair_coeff * * AlO.streitz Al O :pre
pair_style tip4p/cut 1 2 7 8 0.15 12.0
pair_coeff * * :pre
@ -85,6 +91,8 @@ the 2 atoms, and epsilon is the dielectric constant which can be set
by the "dielectric"_dielectric.html command. The cutoff Rc truncates
the interaction distance.
:line
Style {coul/debye} adds an additional exp() damping factor to the
Coulombic term, given by
@ -93,6 +101,8 @@ Coulombic term, given by
where kappa is the Debye length. This potential is another way to
mimic the screening effect of a polar solvent.
:line
Style {coul/dsf} computes Coulombic interactions via the damped
shifted force model described in "Fennell"_#Fennell, given by:
@ -104,6 +114,8 @@ Wolf model (described below) to provide consistent forces and energies
(the Wolf potential is not differentiable at the cutoff) and smooth
decay to zero.
:line
Style {coul/wolf} computes Coulombic interactions via the Wolf
summation method, described in "Wolf"_#Wolf, given by:
@ -122,6 +134,46 @@ 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.
:line
Style {coul/streitz} is the Coulomb pair interaction defined as part
of the Streitz-Mintmire potential, as described in "this
paper"_#Streitz, in which charge distribution about an atom is modeled
as a Slater 1{s} 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"_pair_eam.html via the "pair_style
hybrid/overlay"_pair_hybrid.html command and charge equilibration must
be performed via the "fix qeq/slater"_fix_qeq.html 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 :pre
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 :pre
Keyword {ewald} does not need a damping parameter, but a
"kspace_style"_kspace_style.html 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"_fix_qeq.html
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.
:line
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
@ -257,3 +309,7 @@ Phys, 110, 8254 (1999).
:link(Fennell)
[(Fennell)] C. J. Fennell, J. D. Gezelter, J Chem Phys, 124,
234104 (2006).
:link(Streitz)
[(Streitz)] F. H. Streitz, J. W. Minimire, Phys Rev B 50,
11996-12003 (1994).