2006-09-22 00:22:34 +08:00
|
|
|
<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 eam command
|
|
|
|
</H3>
|
2007-02-13 02:36:07 +08:00
|
|
|
<H3>pair_style eam/opt command
|
|
|
|
</H3>
|
2006-09-22 00:22:34 +08:00
|
|
|
<H3>pair_style eam/alloy command
|
|
|
|
</H3>
|
2007-02-13 02:36:07 +08:00
|
|
|
<H3>pair_style eam/alloy/opt command
|
|
|
|
</H3>
|
2009-11-06 03:59:04 +08:00
|
|
|
<H3>pair_style eam/cd command
|
|
|
|
</H3>
|
2006-09-22 00:22:34 +08:00
|
|
|
<H3>pair_style eam/fs command
|
|
|
|
</H3>
|
2007-02-13 02:36:07 +08:00
|
|
|
<H3>pair_style eam/fs/opt command
|
|
|
|
</H3>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P><B>Syntax:</B>
|
|
|
|
</P>
|
|
|
|
<PRE>pair_style style
|
|
|
|
</PRE>
|
2009-11-06 03:59:04 +08:00
|
|
|
<UL><LI>style = <I>eam</I> or <I>eam/alloy</I> or <I>eam/cd</I> or <I>eam/fs</I> or <I>eam/opt</I> or <I>eam/alloy/opt</I> or <I>eam/fs/opt</I>
|
2006-09-22 00:22:34 +08:00
|
|
|
</UL>
|
|
|
|
<P><B>Examples:</B>
|
|
|
|
</P>
|
|
|
|
<PRE>pair_style eam
|
2007-02-10 05:40:32 +08:00
|
|
|
pair_style eam/opt
|
2006-09-22 00:22:34 +08:00
|
|
|
pair_coeff * * cuu3
|
2006-11-02 07:01:32 +08:00
|
|
|
pair_coeff 1*3 1*3 niu3.eam
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
|
|
|
<PRE>pair_style eam/alloy
|
2007-02-10 05:40:32 +08:00
|
|
|
pair_style eam/alloy/opt
|
2006-11-02 07:01:32 +08:00
|
|
|
pair_coeff * * ../potentials/nialhjea.eam.alloy Ni Al Ni Ni
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
2009-11-06 03:59:04 +08:00
|
|
|
<PRE>pair_style eam/cd
|
|
|
|
pair_coeff * * ../potentials/FeCr.cdeam Fe Cr
|
|
|
|
</PRE>
|
2006-09-22 00:22:34 +08:00
|
|
|
<PRE>pair_style eam/fs
|
2007-02-10 05:40:32 +08:00
|
|
|
pair_style eam/fs/opt
|
2006-11-02 07:01:32 +08:00
|
|
|
pair_coeff * * nialhjea.eam.fs Ni Al Ni Ni
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
|
|
|
<P><B>Description:</B>
|
|
|
|
</P>
|
|
|
|
<P>Style <I>eam</I> computes pairwise interactions for metals and metal alloys
|
|
|
|
using embedded-atom method (EAM) potentials <A HREF = "#Daw">(Daw)</A>. The total
|
|
|
|
energy Ei of an atom I is given by
|
|
|
|
</P>
|
|
|
|
<CENTER><IMG SRC = "Eqs/pair_eam.jpg">
|
|
|
|
</CENTER>
|
|
|
|
<P>where F is the embedding energy which is a function of the atomic
|
|
|
|
electron density rho, phi is a pair potential interaction, and alpha
|
|
|
|
and beta are the element types of atoms I and J. The multi-body
|
|
|
|
nature of the EAM potential is a result of the embedding energy term.
|
|
|
|
Both summations in the formula are over all neighbors J of atom I
|
|
|
|
within the cutoff distance.
|
|
|
|
</P>
|
2007-02-10 05:40:32 +08:00
|
|
|
<P>Style <I>eam/opt</I> is an optimized version of style <I>eam</I> that should
|
|
|
|
give identical answers. Depending on system size and the processor
|
|
|
|
you are running on, it may be 5-25% faster (for the pairwise portion
|
|
|
|
of the run time).
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>The cutoff distance and the tabulated values of the functionals F,
|
|
|
|
rho, and phi are listed in one or more files which are specified by
|
|
|
|
the <A HREF = "pair_coeff.html">pair_coeff</A> command. These are ASCII text files
|
2008-11-17 22:56:58 +08:00
|
|
|
in a DYNAMO-style format which is described below. DYNAMO was the
|
|
|
|
original serial EAM MD code, written by the EAM originators. Several
|
|
|
|
DYNAMO potential files for different metals are included in the
|
|
|
|
"potentials" directory of the LAMMPS distribution. All of these files
|
|
|
|
are parameterized in terms of LAMMPS <A HREF = "units.html">metal units</A>.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<P>IMPORTANT NOTE: The <I>eam</I> style reads single-element EAM potentials in
|
2006-09-28 03:12:31 +08:00
|
|
|
the DYNAMO <I>funcfl</I> format. Either single element or alloy systems
|
2006-11-02 07:01:32 +08:00
|
|
|
can be modeled using multiple <I>funcfl</I> files and style <I>eam</I>. For the
|
|
|
|
alloy case LAMMPS mixes the single-element potentials to produce alloy
|
|
|
|
potentials, the same way that DYNAMO does. Alternatively, a single
|
2007-03-08 09:01:08 +08:00
|
|
|
DYNAMO <I>setfl</I> file or Finnis/Sinclair EAM file can be used by LAMMPS
|
2009-11-06 03:59:04 +08:00
|
|
|
to model alloy systems by invoking the <I>eam/alloy</I> or <I>eam/cd</I> or
|
|
|
|
<I>eam/fs</I> styles as described below. These files require no mixing
|
|
|
|
since they specify alloy interactions explicitly.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2010-08-22 05:17:17 +08:00
|
|
|
<P>Note that unlike for other potentials, cutoffs for EAM potentials are
|
|
|
|
not set in the pair_style or pair_coeff command; they are specified in
|
|
|
|
the EAM potential files themselves. Likewise, the EAM potential files
|
|
|
|
list atomic masses; thus you do not need to use the <A HREF = "mass.html">mass</A>
|
|
|
|
command to specify them.
|
|
|
|
</P>
|
2008-11-14 01:11:56 +08:00
|
|
|
<P>There are several WWW sites that distribute and document EAM
|
2008-11-17 22:56:58 +08:00
|
|
|
potentials stored in DYNAMO or other formats:
|
2008-11-14 01:11:56 +08:00
|
|
|
</P>
|
|
|
|
<PRE>http://www.ctcms.nist.gov/potentials
|
|
|
|
http://cst-www.nrl.navy.mil/ccm6/ap
|
|
|
|
http://enpub.fulton.asu.edu/cms/potentials/main/main.htm
|
|
|
|
</PRE>
|
|
|
|
<P>These potentials should be usable with LAMMPS, though the alternate
|
|
|
|
formats would need to be converted to the DYNAMO format used by LAMMPS
|
2009-01-14 22:29:55 +08:00
|
|
|
and described on this page. The NIST site is maintained by Chandler
|
|
|
|
Becker (cbecker at nist.gov) who is good resource for info on
|
|
|
|
interatomic potentials and file formats.
|
2008-11-14 01:11:56 +08:00
|
|
|
</P>
|
|
|
|
<HR>
|
|
|
|
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>For style <I>eam</I>, potential values are read from a file that is in the
|
|
|
|
DYNAMO single-element <I>funcfl</I> format. If the DYNAMO file was created
|
|
|
|
by a Fortran program, it cannot have "D" values in it for exponents.
|
|
|
|
C only recognizes "e" or "E" for scientific notation.
|
|
|
|
</P>
|
2006-11-02 07:01:32 +08:00
|
|
|
<P>Note that unlike for other potentials, cutoffs for EAM potentials are
|
|
|
|
not set in the pair_style or pair_coeff command; they are specified in
|
|
|
|
the EAM potential files themselves.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2006-11-02 07:01:32 +08:00
|
|
|
<P>For style <I>eam</I> a potential file must be assigned to each I,I pair of
|
|
|
|
atom types by using one or more pair_coeff commands, each with a
|
|
|
|
single argument:
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<UL><LI>filename
|
|
|
|
</UL>
|
|
|
|
<P>Thus the following command
|
|
|
|
</P>
|
2006-11-02 07:01:32 +08:00
|
|
|
<PRE>pair_coeff *2 1*2 cuu3.eam
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
|
|
|
<P>will read the cuu3 potential file and use the tabulated Cu values for
|
|
|
|
F, phi, rho that it contains for type pairs 1,1 and 2,2 (type pairs
|
|
|
|
1,2 and 2,1 are ignored). In effect, this makes atom types 1 and 2 in
|
|
|
|
LAMMPS be Cu atoms. Different single-element files can be assigned to
|
|
|
|
different atom types to model an alloy system. The mixing to create
|
|
|
|
alloy potentials for type pairs with I != J is done automatically the
|
2008-03-01 09:13:20 +08:00
|
|
|
same way that the serial DYNAMO code originally did it; you do not
|
2006-09-22 00:22:34 +08:00
|
|
|
need to specify coefficients for these type pairs.
|
|
|
|
</P>
|
2006-11-04 04:18:04 +08:00
|
|
|
<P><I>Funcfl</I> files in the <I>potentials</I> directory of the LAMMPS
|
|
|
|
distribution have an ".eam" suffix. A DYNAMO single-element <I>funcfl</I>
|
|
|
|
file is formatted as follows:
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<UL><LI>line 1: comment (ignored)
|
|
|
|
<LI>line 2: atomic number, mass, lattice constant, lattice type (e.g. FCC)
|
|
|
|
<LI>line 3: Nrho, drho, Nr, dr, cutoff
|
|
|
|
</UL>
|
|
|
|
<P>On line 2, all values but the mass are ignored by LAMMPS. The mass is
|
2010-12-07 23:26:24 +08:00
|
|
|
in mass <A HREF = "units.html">units</A>, e.g. mass number or grams/mole for metal
|
|
|
|
units. The cubic lattice constant is in Angstroms. On line 3, Nrho
|
2007-06-20 20:56:17 +08:00
|
|
|
and Nr are the number of tabulated values in the subsequent arrays,
|
|
|
|
drho and dr are the spacing in density and distance space for the
|
|
|
|
values in those arrays, and the specified cutoff becomes the pairwise
|
|
|
|
cutoff used by LAMMPS for the potential. The units of dr are
|
|
|
|
Angstroms; I'm not sure of the units for drho - some measure of
|
|
|
|
electron density.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2008-03-01 09:13:20 +08:00
|
|
|
<P>Following the three header lines are three arrays of tabulated values:
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2006-11-02 07:01:32 +08:00
|
|
|
<UL><LI>embedding function F(rho) (Nrho values)
|
|
|
|
<LI>effective charge function Z(r) (Nr values)
|
|
|
|
<LI>density function rho(r) (Nr values)
|
2006-09-22 00:22:34 +08:00
|
|
|
</UL>
|
|
|
|
<P>The values for each array can be listed as multiple values per line,
|
2006-11-02 07:01:32 +08:00
|
|
|
so long as each array starts on a new line. For example, the
|
|
|
|
individual Z(r) values are for r = 0,dr,2*dr, ... (Nr-1)*dr.
|
|
|
|
</P>
|
|
|
|
<P>The units for the embedding function F are eV. The units for the
|
|
|
|
density function rho are the same as for drho (see above, electron
|
|
|
|
density). The units for the effective charge Z are "atomic charge" or
|
2008-03-01 09:13:20 +08:00
|
|
|
sqrt(Hartree * Bohr-radii). For two interacting atoms i,j this is used
|
2006-11-02 07:01:32 +08:00
|
|
|
by LAMMPS to compute the pair potential term in the EAM energy
|
|
|
|
expression as r*phi, in units of eV-Angstroms, via the formula
|
|
|
|
</P>
|
|
|
|
<PRE>r*phi = 27.2 * 0.529 * Zi * Zj
|
|
|
|
</PRE>
|
|
|
|
<P>where 1 Hartree = 27.2 eV and 1 Bohr = 0.529 Angstroms.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<HR>
|
|
|
|
|
|
|
|
<P>Style <I>eam/alloy</I> computes pairwise interactions using the same
|
|
|
|
formula as style <I>eam</I>. However the associated
|
|
|
|
<A HREF = "pair_coeff.html">pair_coeff</A> command reads a DYNAMO <I>setfl</I> file
|
|
|
|
instead of a <I>funcfl</I> file. <I>Setfl</I> files can be used to model a
|
|
|
|
single-element or alloy system. In the alloy case, as explained
|
|
|
|
above, <I>setfl</I> files contain explicit tabulated values for alloy
|
|
|
|
interactions. Thus they allow more generality than <I>funcfl</I> files for
|
|
|
|
modeling alloys.
|
|
|
|
</P>
|
2007-02-10 05:40:32 +08:00
|
|
|
<P>Style <I>eam/alloy/opt</I> is an optimized version of style <I>eam/alloy</I>
|
|
|
|
that should give identical answers. Depending on system size and the
|
|
|
|
processor you are running on, it may be 5-25% faster (for the pairwise
|
|
|
|
portion of the run time).
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>For style <I>eam/alloy</I>, potential values are read from a file that is
|
2006-11-02 07:01:32 +08:00
|
|
|
in the DYNAMO multi-element <I>setfl</I> format, except that element names
|
|
|
|
(Ni, Cu, etc) are added to one of the lines in the file. If the
|
|
|
|
DYNAMO file was created by a Fortran program, it cannot have "D"
|
|
|
|
values in it for exponents. C only recognizes "e" or "E" for
|
|
|
|
scientific notation.
|
|
|
|
</P>
|
2006-11-04 01:09:44 +08:00
|
|
|
<P>Only a single pair_coeff command is used with the <I>eam/alloy</I> style
|
|
|
|
which specifies a DYNAMO <I>setfl</I> file, which contains information for
|
|
|
|
M 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:
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<UL><LI>filename
|
2006-11-02 07:01:32 +08:00
|
|
|
<LI>N element names = mapping of <I>setfl</I> elements to atom types
|
2006-09-22 00:22:34 +08:00
|
|
|
</UL>
|
2006-11-04 01:09:44 +08:00
|
|
|
<P>As an example, the potentials/nialhjea <I>setfl</I> file has tabulated EAM
|
|
|
|
values for 3 elements and their alloy interactions: Ni, Al, and H. If
|
|
|
|
your LAMMPS simulation has 4 atoms types and you want the 1st 3 to be
|
|
|
|
Ni, and the 4th to be Al, you would use the following pair_coeff
|
|
|
|
command:
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2006-11-02 07:01:32 +08:00
|
|
|
<PRE>pair_coeff * * nialhjea.eam.alloy Ni Ni Ni Al
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
|
|
|
<P>The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
|
2006-11-02 07:01:32 +08:00
|
|
|
The first three Ni arguments map LAMMPS atom types 1,2,3 to the Ni
|
|
|
|
element in the <I>setfl</I> file. The final Al argument maps LAMMPS atom
|
2006-11-04 01:09:44 +08:00
|
|
|
type 4 to the Al element in the <I>setfl</I> file. Note that there is no
|
|
|
|
requirement that your simulation use all the elements specified by the
|
|
|
|
<I>setfl</I> file.
|
|
|
|
</P>
|
|
|
|
<P>If a mapping value is specified as NULL, the mapping is not performed.
|
|
|
|
This can be used when an <I>eam/alloy</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.
|
2006-09-28 03:12:31 +08:00
|
|
|
</P>
|
|
|
|
<P><I>Setfl</I> files in the <I>potentials</I> directory of the LAMMPS distribution
|
2006-11-04 04:18:04 +08:00
|
|
|
have an ".eam.alloy" suffix. A DYNAMO multi-element <I>setfl</I> file is
|
2006-09-22 00:22:34 +08:00
|
|
|
formatted as follows:
|
|
|
|
</P>
|
|
|
|
<UL><LI>lines 1,2,3 = comments (ignored)
|
2006-11-02 07:01:32 +08:00
|
|
|
<LI>line 4: Nelements Element1 Element2 ... ElementN
|
2006-09-22 00:22:34 +08:00
|
|
|
<LI>line 5: Nrho, drho, Nr, dr, cutoff
|
|
|
|
</UL>
|
2006-11-02 07:01:32 +08:00
|
|
|
<P>In a DYNAMO <I>setfl</I> file, line 4 only lists Nelements = the # of
|
|
|
|
elements in the <I>setfl</I> file. For LAMMPS, the element name (Ni, Cu,
|
|
|
|
etc) of each element must be added to the line, in the order the
|
|
|
|
elements appear in the file.
|
|
|
|
</P>
|
|
|
|
<P>The meaning and units of the values in line 5 is the same as for the
|
|
|
|
<I>funcfl</I> file described above. Note that the cutoff (in Angstroms) is
|
|
|
|
a global value, valid for all pairwise interactions for all element
|
|
|
|
pairings.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<P>Following the 5 header lines are Nelements sections, one for each
|
|
|
|
element, each with the following format:
|
|
|
|
</P>
|
|
|
|
<UL><LI>line 1 = atomic number, mass, lattice constant, lattice type (e.g. FCC)
|
2006-11-02 07:01:32 +08:00
|
|
|
<LI>embedding function F(rho) (Nrho values)
|
|
|
|
<LI>density function rho(r) (Nr values)
|
2006-09-22 00:22:34 +08:00
|
|
|
</UL>
|
2010-12-07 23:26:24 +08:00
|
|
|
<P>As with the <I>funcfl</I> files, only the mass (in mass <A HREF = "units.html">units</A>,
|
|
|
|
e.g. mass number or grams/mole for metal units) is used by LAMMPS from
|
|
|
|
the 1st line. The cubic lattice constant is in Angstroms. The F and
|
|
|
|
rho arrays are unique to a single element and have the same format and
|
|
|
|
units as in a <I>funcfl</I> file.
|
2006-11-02 07:01:32 +08:00
|
|
|
</P>
|
|
|
|
<P>Following the Nelements sections, Nr values for each pair potential
|
|
|
|
phi(r) array are listed for all i,j element pairs in the same format
|
|
|
|
as other arrays. Since these interactions are symmetric (i,j = j,i)
|
|
|
|
only phi arrays with i >= j are listed, in the following order: i,j =
|
2006-09-22 00:22:34 +08:00
|
|
|
(1,1), (2,1), (2,2), (3,1), (3,2), (3,3), (4,1), ..., (Nelements,
|
2006-11-02 07:01:32 +08:00
|
|
|
Nelements). Unlike the effective charge array Z(r) in <I>funcfl</I> files,
|
|
|
|
the tabulated values for each phi function are listed in <I>setfl</I> files
|
|
|
|
directly as r*phi (in units of eV-Angstroms), since they are for atom
|
|
|
|
pairs.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<HR>
|
|
|
|
|
2009-11-06 03:59:04 +08:00
|
|
|
<P>Style <I>eam/cd</I> is similar to the <I>eam/alloy</I> style, except that it
|
|
|
|
computes alloy pairwise interactions using the concentration-dependent
|
|
|
|
embedded-atom method (CD-EAM). This model can reproduce the enthalpy
|
|
|
|
of mixing of alloys over the full composition range, as described in
|
|
|
|
<A HREF = "#Stukowski">(Stukowski)</A>.
|
|
|
|
</P>
|
|
|
|
<P>The pair_coeff command is specified the same as for the <I>eam/alloy</I>
|
|
|
|
style. However the DYNAMO <I>setfl</I> file must has two
|
|
|
|
lines added to it, at the end of the file:
|
|
|
|
</P>
|
|
|
|
<UL><LI>line 1: Comment line (ignored)
|
|
|
|
<LI>line 2: N Coefficient0 Coefficient1 ... CoeffincientN
|
|
|
|
</UL>
|
|
|
|
<P>The last line begins with the degree <I>N</I> of the polynomial function
|
|
|
|
<I>h(x)</I> that modifies the cross interaction between A and B elements.
|
|
|
|
Then <I>N+1</I> coefficients for the terms of the polynomial are then
|
|
|
|
listed.
|
|
|
|
</P>
|
|
|
|
<P>Modified EAM <I>setfl</I> files used with the <I>eam/cd</I> style must contain
|
2009-11-06 23:25:30 +08:00
|
|
|
exactly two elements, i.e. in the current implementation the <I>eam/cd</I>
|
2009-11-06 03:59:04 +08:00
|
|
|
style only supports binary alloys. The first and second elements in
|
|
|
|
the input EAM file are always taken as the <I>A</I> and <I>B</I> species.
|
|
|
|
</P>
|
|
|
|
<P><I>CD-EAM</I> files in the <I>potentials</I> directory of the LAMMPS
|
|
|
|
distribution have a ".cdeam" suffix.
|
|
|
|
</P>
|
|
|
|
<HR>
|
|
|
|
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>Style <I>eam/fs</I> computes pairwise interactions for metals and metal
|
|
|
|
alloys using a generalized form of EAM potentials due to Finnis and
|
|
|
|
Sinclair <A HREF = "#Finnis">(Finnis)</A>. The total energy Ei of an atom I is
|
|
|
|
given by
|
|
|
|
</P>
|
|
|
|
<CENTER><IMG SRC = "Eqs/pair_eam_fs.jpg">
|
|
|
|
</CENTER>
|
|
|
|
<P>This has the same form as the EAM formula above, except that rho is
|
|
|
|
now a functional specific to the atomic types of both atoms I and J,
|
|
|
|
so that different elements can contribute differently to the total
|
|
|
|
electron density at an atomic site depending on the identity of the
|
|
|
|
element at that atomic site.
|
|
|
|
</P>
|
2007-02-10 05:40:32 +08:00
|
|
|
<P>Style <I>eam/fs/opt</I> is an optimized version of style <I>eam/fs</I> that
|
|
|
|
should give identical answers. Depending on system size and the
|
|
|
|
processor you are running on, it may be 5-25% faster (for the pairwise
|
|
|
|
portion of the run time).
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>The associated <A HREF = "pair_coeff.html">pair_coeff</A> command for style <I>eam/fs</I>
|
|
|
|
reads a DYNAMO <I>setfl</I> file that has been extended to include
|
2006-11-04 04:18:04 +08:00
|
|
|
additional rho_alpha_beta arrays of tabulated values. A discussion of
|
|
|
|
how FS EAM differs from conventional EAM alloy potentials is given in
|
|
|
|
<A HREF = "#Ackland1">(Ackland1)</A>. An example of such a potential is the same
|
|
|
|
author's Fe-P FS potential <A HREF = "#Ackland2">(Ackland2)</A>. Note that while FS
|
|
|
|
potentials always specify the embedding energy with a square root
|
|
|
|
dependence on the total density, the implementation in LAMMPS does not
|
|
|
|
require that; the user can tabulate any functional form desired in the
|
|
|
|
FS potential files.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<P>For style <I>eam/fs</I>, the form of the pair_coeff command is exactly the
|
|
|
|
same as for style <I>eam/alloy</I>, e.g.
|
|
|
|
</P>
|
2006-11-02 07:01:32 +08:00
|
|
|
<PRE>pair_coeff * * nialhjea.eam.fs Ni Ni Ni Al
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
|
|
|
<P>where there are N additional arguments after the filename, where N is
|
|
|
|
the number of LAMMPS atom types. The N values determine the mapping
|
2006-09-28 03:12:31 +08:00
|
|
|
of LAMMPS atom types to EAM elements in the file, as described above
|
|
|
|
for style <I>eam/alloy</I>. As with <I>eam/alloy</I>, if a mapping value is
|
2006-11-02 07:01:32 +08:00
|
|
|
NULL, the mapping is not performed. This can be used when an <I>eam/fs</I>
|
|
|
|
potential is used as part of the <I>hybrid</I> pair style. The NULL values
|
2006-09-28 03:12:31 +08:00
|
|
|
are used as placeholders for atom types that will be used with other
|
|
|
|
potentials.
|
|
|
|
</P>
|
|
|
|
<P>FS EAM files include more information than the DYNAMO <I>setfl</I> format
|
2006-11-02 07:01:32 +08:00
|
|
|
files read by <I>eam/alloy</I>, in that i,j density functionals for all
|
2006-09-28 03:12:31 +08:00
|
|
|
pairs of elements are included as needed by the Finnis/Sinclair
|
|
|
|
formulation of the EAM.
|
|
|
|
</P>
|
|
|
|
<P>FS EAM files in the <I>potentials</I> directory of the LAMMPS distribution
|
2006-11-02 07:01:32 +08:00
|
|
|
have an ".eam.fs" suffix. They are formatted as follows:
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<UL><LI>lines 1,2,3 = comments (ignored)
|
2006-11-02 07:01:32 +08:00
|
|
|
<LI>line 4: Nelements Element1 Element2 ... ElementN
|
2006-09-22 00:22:34 +08:00
|
|
|
<LI>line 5: Nrho, drho, Nr, dr, cutoff
|
|
|
|
</UL>
|
|
|
|
<P>The 5-line header section is identical to an EAM <I>setfl</I> file.
|
|
|
|
</P>
|
|
|
|
<P>Following the header are Nelements sections, one for each element I,
|
|
|
|
each with the following format:
|
|
|
|
</P>
|
|
|
|
<UL><LI>line 1 = atomic number, mass, lattice constant, lattice type (e.g. FCC)
|
2006-11-02 07:01:32 +08:00
|
|
|
<LI>embedding function F(rho) (Nrho values)
|
|
|
|
<LI>density function rho(r) for element I at element 1 (Nr values)
|
|
|
|
<LI>density function rho(r) for element I at element 2
|
2006-09-22 00:22:34 +08:00
|
|
|
<LI>...
|
2006-11-02 07:01:32 +08:00
|
|
|
<LI>density function rho(r) for element I at element Nelement
|
2006-09-22 00:22:34 +08:00
|
|
|
</UL>
|
2006-11-02 07:01:32 +08:00
|
|
|
<P>The units of these quantities in line 1 are the same as for <I>setfl</I>
|
|
|
|
files. Note that the rho(r) arrays in Finnis/Sinclair can be
|
|
|
|
asymmetric (i,j != j,i) so there are Nelements^2 of them listed in the
|
|
|
|
file.
|
|
|
|
</P>
|
|
|
|
<P>Following the Nelements sections, Nr values for each pair potential
|
|
|
|
phi(r) array are listed in the same manner (r*phi, units of
|
|
|
|
eV-Angstroms) as in EAM <I>setfl</I> files. Note that in Finnis/Sinclair,
|
|
|
|
the phi(r) arrays are still symmetric, so only phi arrays for i >= j
|
|
|
|
are listed.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<HR>
|
|
|
|
|
2008-01-22 02:12:34 +08:00
|
|
|
<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
|
2007-06-25 22:36:36 +08:00
|
|
|
</P>
|
2007-06-26 08:03:39 +08:00
|
|
|
<P>For atom type pairs I,J and I != J, where types I and J correspond to
|
|
|
|
two different element types, mixing is performed by LAMMPS as
|
2007-06-25 22:36:36 +08:00
|
|
|
described above with the individual styles. You never need to specify
|
|
|
|
a pair_coeff command with I != J arguments for the eam styles.
|
|
|
|
</P>
|
|
|
|
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
|
2007-06-26 08:03:39 +08:00
|
|
|
shift, table, and tail options.
|
2007-06-25 22:36:36 +08:00
|
|
|
</P>
|
2007-06-26 08:03:39 +08:00
|
|
|
<P>The eam pair styles do not write their information to <A HREF = "restart.html">binary restart
|
2008-10-09 22:47:45 +08:00
|
|
|
files</A>, since it is stored in tabulated potential files.
|
|
|
|
Thus, you need to re-specify the pair_style and pair_coeff commands in
|
|
|
|
an input script that reads a restart file.
|
2007-06-25 22:36:36 +08:00
|
|
|
</P>
|
2007-10-04 08:21:14 +08:00
|
|
|
<P>The eam pair styles 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
|
2007-10-12 07:09:49 +08:00
|
|
|
<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
|
2007-10-04 08:21:14 +08:00
|
|
|
</P>
|
2007-06-25 22:36:36 +08:00
|
|
|
<HR>
|
|
|
|
|
2007-02-10 05:40:32 +08:00
|
|
|
<P><B>Restrictions:</B>
|
|
|
|
</P>
|
2009-11-06 03:59:04 +08:00
|
|
|
<P>All of these styles except those ending in <I>opt</I> and the <I>eam/cd</I>
|
|
|
|
style are part of the "manybody" package. They are only enabled if
|
|
|
|
LAMMPS was built with that package (which it is by default).
|
|
|
|
</P>
|
|
|
|
<P>The styles ending in <I>opt</I> are part of the "opt" package and also
|
|
|
|
require the "manybody" package. They are only enabled if LAMMPS was
|
|
|
|
built with those packages. See the <A HREF = "Section_start.html#2_3">Making
|
|
|
|
LAMMPS</A> section for more info.
|
|
|
|
</P>
|
|
|
|
<P>The <I>eam/cd</I> style is part of the "user-cd-eam" package and also
|
|
|
|
requires the "manybody" package. It is only enabled if LAMMPS was
|
|
|
|
built with those packages. See the <A HREF = "Section_start.html#2_3">Making
|
|
|
|
LAMMPS</A> section for more info.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
<P><B>Related commands:</B>
|
|
|
|
</P>
|
|
|
|
<P><A HREF = "pair_coeff.html">pair_coeff</A>
|
|
|
|
</P>
|
|
|
|
<P><B>Default:</B> none
|
|
|
|
</P>
|
|
|
|
<HR>
|
|
|
|
|
|
|
|
<A NAME = "Ackland1"></A>
|
|
|
|
|
|
|
|
<P><B>(Ackland1)</B> Ackland, Condensed Matter (2005).
|
|
|
|
</P>
|
|
|
|
<A NAME = "Ackland2"></A>
|
|
|
|
|
|
|
|
<P><B>(Ackland2)</B> Ackland, Mendelev, Srolovitz, Han and Barashev, Journal
|
|
|
|
of Physics: Condensed Matter, 16, S2629 (2004).
|
|
|
|
</P>
|
|
|
|
<A NAME = "Daw"></A>
|
|
|
|
|
|
|
|
<P><B>(Daw)</B> Daw, Baskes, Phys Rev Lett, 50, 1285 (1983).
|
|
|
|
Daw, Baskes, Phys Rev B, 29, 6443 (1984).
|
|
|
|
</P>
|
|
|
|
<A NAME = "Finnis"></A>
|
|
|
|
|
|
|
|
<P><B>(Finnis)</B> Finnis, Sinclair, Philosophical Magazine A, 50, 45 (1984).
|
|
|
|
</P>
|
2009-11-06 03:59:04 +08:00
|
|
|
<A NAME = "Stukowski"></A>
|
|
|
|
|
|
|
|
<P><B>(Stukowski)</B> Stukowski, Sadigh, Erhart, Caro; Modeling Simulation
|
|
|
|
Materials Science & Engineering, 7, 075005 (2009).
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
</HTML>
|