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Added equation for ZBL 

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@10796 f3b2605a-c512-4ea7-a41b-209d697bcdaa
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athomps 2013-09-17 19:07:59 +00:00
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1 changed files with 35 additions and 19 deletions
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doc/pair_zbl.txt
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@ -23,35 +23,51 @@ pair_coeff 1 1 14.0 :pre
[Description:] [Description:]
Style {zbl} computes the Zeigler-Biersack-Littmark (ZBL) repulsive Style {zbl} computes the Ziegler-Biersack-Littmark (ZBL) screened nuclear
interaction for describing high-energy collisions between atoms. repulsion for describing high-energy collisions between atoms.
"(Zeigler)"_#Zeigler. It includes an additional switching function "(Ziegler)"_#Ziegler. It includes an additional switching function
S(r) that ramps the energy, force, and curvature smoothly to zero that ramps the energy, force, and curvature smoothly to zero
between an inner and outer cutoff. The switching function is the same between an inner and outer cutoff. The potential
one used in "pair_style lj/gromacs"_pair_gromacs.html. energy due to a pair of atoms at a distance r_ij is given by:
The inner and outer cutoff are the same for all pairs of :c,image(Eqs/pair_zbl.jpg)
atom types.
The following coefficient must be defined for each pair of atoms types where e is the electron
charge, epsilon_0 is the electrical permittivity of vacuum, and
Z_i and Z_j are the nuclear charges of the two atoms in electron
charge units.
The switching
function S(r) is identical to that used by
"pair_style lj/gromacs"_pair_gromacs.html.
Here, the inner and outer cutoff are the same
for all pairs of atom types.
The following coefficient must be defined for each pair of atom types
via the "pair_coeff"_pair_coeff.html command as in the examples above, via the "pair_coeff"_pair_coeff.html command as in the examples above,
or in the data file or restart files read by the or in the LAMMPS data file.
"read_data"_read_data.html or "read_restart"_read_restart.html Z can not be specified for two different atoms types.
commands: Therefore the lists of atom types I and atom types J must match.
Z (dimensionless) :ul Z (electron charge) :ul
Although Z must be defined for all atom type pairs I,J, it is only Although Z must be defined for all atom type pairs I,J, it is only
stored for individual atom types, i.e. when I = J. Z is usually taken stored for individual atom types, i.e. when I = J. Z is normally equal
to be the atomic number of the element that corresponds to the atom to the atomic number of the atom type.
type.
IMPORTANT NOTE: The numerical values of the exponential decay
constants in the screening function depend
on the unit of distance. In the above equation they are given for
units of angstroms. LAMMPS will automatically convert these values to
the distance unit of the specified LAMMPS "units"_units.html setting.
The values of Z should always be given in units of electron charge.
:line :line
[Mixing, shift, table, tail correction, restart, rRESPA info]: [Mixing, shift, table, tail correction, restart, rRESPA info]:
For atom type pairs I,J and I != J, the ZBL interaction For atom type pairs I,J and I != J, the ZBL interaction
is defined by the values of Z for the two atom types. is defined by the values of Z for the two atom types, as in
the equation above.
The ZBL pair style does not support the The ZBL pair style does not support the
"pair_modify"_pair_modify.html shift option, since the ZBL "pair_modify"_pair_modify.html shift option, since the ZBL
@ -86,6 +102,6 @@ support the {inner}, {middle}, {outer} keywords.
:line :line
:link(Zeigler) :link(Ziegler)
[(Zeigler)] J.F. Zeigler, J. P. Biersack and U. Littmark, "The [(Ziegler)] J.F. Ziegler, J. P. Biersack and U. Littmark, "The
Stopping and Range of Ions in Matter," Volume 1, Pergamon, 1985. Stopping and Range of Ions in Matter," Volume 1, Pergamon, 1985.