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rLAMMPS lammps
pair_meam_spline.html
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<HTML>
<CENTER><A
HREF =
"http://lammps.sandia.gov"
>
LAMMPS WWW Site
</A>
-
<A
HREF =
"Manual.html"
>
LAMMPS Documentation
</A>
-
<A
HREF =
"Section_commands.html#comm"
>
LAMMPS Commands
</A>
</CENTER>
<HR>
<H3>
pair_style meam/spline
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
pair_style meam/spline
</PRE>
<P><B>
Examples:
</B>
</P>
<PRE>
pair_style meam/spline
pair_coeff * * Ti.meam.spline Ti
pair_coeff * * Ti.meam.spline Ti Ti Ti
</PRE>
<P><B>
Description:
</B>
</P>
<P>
The
<I>
meam/spline
</I>
style computes pairwise interactions for metals
using a variant of modified embedded-atom method (MEAM) potentials
<A
HREF =
"#Lenosky"
>
(Lenosky)
</A>
. The total energy E is given by
</P>
<CENTER><IMG
SRC =
"Eqs/pair_meam_spline.jpg"
>
</CENTER>
<P>
where rho_i is the density at atom I, theta_jik is the angle between
atoms J, I, and K centered on atom I. The five functions Phi, U, rho,
f, and g are represented by cubic splines.
</P>
<P>
The cutoffs and the coefficients for these spline functions are listed
in a parameter file which is specified by the
<A
HREF =
"pair_coeff.html"
>
pair_coeff
</A>
command. Parameter files for different
elements are included in the "potentials" directory of the LAMMPS
distribution and have a ".meam.spline" file suffix. All of these
files are parameterized in terms of LAMMPS
<A
HREF =
"units.html"
>
metal units
</A>
.
</P>
<P>
Note that unlike for other potentials, cutoffs for spline-based MEAM
potentials are not set in the pair_style or pair_coeff command; they
are specified in the potential files themselves.
</P>
<P>
Unlike the EAM pair style, which retrieves the atomic mass from the
potential file, the spline-based MEAM potentials do not include mass
information; thus you need to use the
<A
HREF =
"mass.html"
>
mass
</A>
command to
specify it.
</P>
<P>
Only a single pair_coeff command is used with the
<I>
meam/spline
</I>
style
which specifies a potential file with parameters for all needed
elements. These are mapped to LAMMPS atom types by specifying N
additional arguments after the filename in the pair_coeff command,
where N is the number of LAMMPS atom types:
</P>
<UL><LI>
filename
<LI>
N element names = mapping of spline-based MEAM elements to atom types
</UL>
<P>
As an example, imagine the Ti.meam.spline file has values for Ti. If
your LAMMPS simulation has 3 atoms types and they are all to be
treated with this potentials, you would use the following pair_coeff
command:
</P>
<PRE>
pair_coeff * * Ti.meam.spline Ti Ti Ti
</PRE>
<P>
The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
The three Ti arguments map LAMMPS atom types 1,2,3 to the Ti element
in the potential file. If a mapping value is specified as NULL, the
mapping is not performed. This can be used when a
<I>
meam/spline
</I>
potential is used as part of the
<I>
hybrid
</I>
pair style. The NULL values
are placeholders for atom types that will be used with other
potentials.
</P>
<P>
IMPORTANT NOTE: The
<I>
meam/spline
</I>
style currently supports only
single-element MEAM potentials. It may be extended for alloy systems
in the future.
</P>
<HR>
<P><B>
Mixing, shift, table, tail correction, restart, rRESPA info
</B>
:
</P>
<P>
The current version of this pair style does not support multiple
element types or mixing. It has been designed for pure elements only.
</P>
<P>
This pair style does not support the
<A
HREF =
"pair_modify.html"
>
pair_modify
</A>
shift, table, and tail options.
</P>
<P>
The
<I>
meam/spline
</I>
pair style does not write its information to
<A
HREF =
"restart.html"
>
binary
restart files
</A>
, since it is stored in an external
potential parameter file. Thus, you need to re-specify the pair_style
and pair_coeff commands in an input script that reads a restart file.
</P>
<P>
The
<I>
meam/spline
</I>
pair style can only be used via the
<I>
pair
</I>
keyword of the
<A
HREF =
"run_style.html"
>
run_style respa
</A>
command. They do not support the
<I>
inner
</I>
,
<I>
middle
</I>
,
<I>
outer
</I>
keywords.
</P>
<HR>
<P><B>
Restrictions:
</B>
</P>
<P>
This pair style requires the
<A
HREF =
"newton.html"
>
newton
</A>
setting to be "on"
for pair interactions.
</P>
<P>
This pair style is only enabled if LAMMPS was built with the USER-MISC
package. See the
<A
HREF =
"Section_start.html#start_3"
>
Making LAMMPS
</A>
section
for more info.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"pair_coeff.html"
>
pair_coeff
</A>
,
<A
HREF =
"pair_meam.html"
>
pair_style meam
</A>
</P>
<P><B>
Default:
</B>
none
</P>
<HR>
<A
NAME =
"Lenosky"
></A>
<P><B>
(Lenosky)
</B>
Lenosky, Sadigh, Alonso, Bulatov, de la Rubia, Kim, Voter,
Kress, Modelling Simulation Materials Science Enginerring, 8, 825
(2000).
</P>
</HTML>
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