lammps/doc/pair_zbl.txt

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

:line

pair_style zbl command :h3

[Syntax:]

pair_style zbl inner outer :pre

inner = distance where switching function begins
outer = global cutoff for ZBL interaction :ul

[Examples:]

pair_style zbl 3.0 4.0
pair_coeff * * 73.0
pair_coeff 1 1 14.0 :pre

[Description:]

Style {zbl} computes the Ziegler-Biersack-Littmark (ZBL) screened nuclear
repulsion for describing high-energy collisions between atoms.
"(Ziegler)"_#Ziegler. It includes an additional switching function 
that ramps the energy, force, and curvature smoothly to zero 
between an inner and outer cutoff. The potential
energy due to a pair of atoms at a distance r_ij is given by:

:c,image(Eqs/pair_zbl.jpg)

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,
or in the LAMMPS data file. 
Z can not be specified for two different atoms types.
Therefore the lists of atom types I and atom types J must match.

Z (electron charge) :ul

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 normally equal
to the atomic number of the atom 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

[Mixing, shift, table, tail correction, restart, rRESPA info]:

For atom type pairs I,J and I != J, the ZBL interaction
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
"pair_modify"_pair_modify.html shift option, since the ZBL
interaction is already smoothed to 0.0 at the
cutoff.

The "pair_modify"_pair_modify.html table option is not relevant
for this pair style.

This pair style does not support the
"pair_modify"_pair_modify.html tail option for adding long-range tail
corrections to energy and pressure, since there are no corrections for
a potential that goes to 0.0 at the cutoff.

This pair style does not write information to "binary
restart files"_restart.html, so pair_style and pair_coeff commands
must be specified in an input script that reads a restart file.

This pair style can only be used via the {pair}
keyword of the "run_style respa"_run_style.html command.  It does not
support the {inner}, {middle}, {outer} keywords.

:line

[Restrictions:] none

[Related commands:]

"pair_coeff"_pair_coeff.html

[Default:] none

:line

:link(Ziegler)
[(Ziegler)] J.F. Ziegler, J. P. Biersack and U. Littmark, "The
Stopping and Range of Ions in Matter," Volume 1, Pergamon, 1985.