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81
doc/pair_tersoff.html
View File

@ -23,8 +23,8 @@ pair_coeff * * SiC.tersoff Si C Si
</PRE>
<P><B>Description:</B>
</P>
<P>The <I>tersoff</I> style computes a 3-body <A HREF = "#Tersoff_1">Tersoff</A> potential
for the energy E of a system of atoms as
<P>The <I>tersoff</I> style computes a 3-body Tersoff potential
<A HREF = "#Tersoff_1">(Tersoff_1)</A> for the energy E of a system of atoms as
</P>
<CENTER><IMG SRC = "Eqs/pair_tersoff_1.jpg">
</CENTER>
@ -104,24 +104,24 @@ in a three-body interaction and it is bonded to the 2nd atom and the
bond is influenced by the 3rd atom. Thus an entry for SiCC means Si
bonded to a C with another C atom influencing the bond. Thus
three-body parameters for SiCSi and SiSiC entries will not, in
general, be the same. The parameters used for the two-body interaction come
from the entry where the 2nd element is repeated. Thus the two-body
parameters for Si interacting with C, comes from the SiCC entry. By
symmetry, the twobody parameters in the SiCC and CSiSi entries should
thus be the same. The parameters used for a particular three-body
interaction come from the entry with the corresponding three elements.
The parameters used only for two-body interactions
(n, beta, lambda2, B, lambda1, and A)
in entries whose 2nd and 3rd element are different (e.g. SiCSi)
are not used for anything and can be set to 0.0 if desired.
general, be the same. The parameters used for the two-body
interaction come from the entry where the 2nd element is repeated.
Thus the two-body parameters for Si interacting with C, comes from the
SiCC entry. By symmetry, the twobody parameters in the SiCC and CSiSi
entries should thus be the same. The parameters used for a particular
three-body interaction come from the entry with the corresponding
three elements. The parameters used only for two-body interactions
(n, beta, lambda2, B, lambda1, and A) in entries whose 2nd and 3rd
element are different (e.g. SiCSi) are not used for anything and can
be set to 0.0 if desired.
</P>
<P>We chose the above form so as to enable users to define
all commonly used variants of the Tersoff potential.
In particular, our form reduces to the original
Tersoff form when m = 3 and gamma = 1, while it reduces to the form of <A HREF = "#Albe">Albe
et al.</A> when beta = 1 and m = 1. Tersoff used a slightly
different but equivalent form for alloys, which we will refer to
as <A HREF = "#Tersoff_2">Tersoff_2</A>.
<P>We chose the above form so as to enable users to define all commonly
used variants of the Tersoff potential. In particular, our form
reduces to the original Tersoff form when m = 3 and gamma = 1, while
it reduces to the form of <A HREF = "#Albe">Albe et al.</A> when beta = 1 and m = 1.
Tersoff used a slightly different but equivalent form for alloys,
which we will refer to as Tersoff_2 potential
<A HREF = "#Tersoff_2">(Tersoff_2)</A>.
</P>
<P>LAMMPS parameter values for Tersoff_2 can be obtained as follows.
The parameters for species i and j can be calculated
@ -129,23 +129,25 @@ using the Tersoff_2 mixing rules:
</P>
<CENTER><IMG SRC = "Eqs/pair_tersoff_2.jpg">
</CENTER>
<P>Values not shown are determined by the first atom type. Finally, the
Tersoff_2 parameters R and S must be converted to the LAMMPS parameters
R and D (R is different in both forms), using the following relations:
R=(R'+S')/2 and D=(S'-R')/2, where the primes indicate the Tersoff_2 parameters.
<P>Values not shown are determined by the first atom type. Finally, the
Tersoff_2 parameters R and S must be converted to the LAMMPS
parameters R and D (R is different in both forms), using the following
relations: R=(R'+S')/2 and D=(S'-R')/2, where the primes indicate the
Tersoff_2 parameters.
</P>
<P>In the potentials directory, the file SiCGe.tersoff
provides the LAMMPS parameters for Tersoff's various versions of Si, as well
as his alloy paramters for Si, C, and Ge. This file can be
used for pure Si, (three different versions), pure C, pure Ge, binary SiC, and binary SiGe.
LAMMPS will generate an error
if this file is used with any combination involving C and Ge, since there are no entries for
the GeC interactions (Tersoff did not publish parameters for this cross-interaction.)
Tersoff files are also provided for the SiC alloy (SiC.tersoff) and the GaN (GaN.tersoff)
alloys.
<P>In the potentials directory, the file SiCGe.tersoff provides the
LAMMPS parameters for Tersoff's various versions of Si, as well as his
alloy paramters for Si, C, and Ge. This file can be used for pure Si,
(three different versions), pure C, pure Ge, binary SiC, and binary
SiGe. LAMMPS will generate an error if this file is used with any
combination involving C and Ge, since there are no entries for the GeC
interactions (Tersoff did not publish parameters for this
cross-interaction.) Tersoff files are also provided for the SiC alloy
(SiC.tersoff) and the GaN (GaN.tersoff) alloys.
</P>
<P>Many thanks to Rutuparna Narulkar, David Farrell, and Xiaowang Zhou for helping clarify
how Tersoff parameters for alloys have been defined in various papers.
<P>Many thanks to Rutuparna Narulkar, David Farrell, and Xiaowang Zhou
for helping clarify how Tersoff parameters for alloys have been
defined in various papers.
</P>
<HR>
@ -200,11 +202,14 @@ appropriate units if your simulation doesn't use "metal" units.
<A NAME = "Tersoff_1"></A>
<A NAME = "Albe"></A><B>(Tersoff_1)</B> J. Tersoff, Phys Rev B, 37, 6991 (1988).
<A NAME = "Tersoff_2"></A><B>(Albe)</B> J. Nord, K. Albe, P. Erhartand K. Nordlund, J. Phys.: Condens. Matter, 15, 5649(2003).
<P><B>(Tersoff_1)</B> J. Tersoff, Phys Rev B, 37, 6991 (1988).
</P>
<A NAME = "Albe"></A>
<P><B>(Albe)</B> J. Nord, K. Albe, P. Erhartand K. Nordlund, J. Phys.:
Condens. Matter, 15, 5649(2003).
</P>
<A NAME = "Tersoff_2"></A>
<P><B>(Tersoff_2)</B> J. Tersoff, Phys Rev B, 39, 5566 (1989)
</P>

75
doc/pair_tersoff.txt
View File

@ -20,8 +20,8 @@ pair_coeff * * SiC.tersoff Si C Si :pre
[Description:]
The {tersoff} style computes a 3-body "Tersoff"_#Tersoff_1 potential
for the energy E of a system of atoms as
The {tersoff} style computes a 3-body Tersoff potential
"(Tersoff_1)"_#Tersoff_1 for the energy E of a system of atoms as
:c,image(Eqs/pair_tersoff_1.jpg)
@ -101,24 +101,24 @@ in a three-body interaction and it is bonded to the 2nd atom and the
bond is influenced by the 3rd atom. Thus an entry for SiCC means Si
bonded to a C with another C atom influencing the bond. Thus
three-body parameters for SiCSi and SiSiC entries will not, in
general, be the same. The parameters used for the two-body interaction come
from the entry where the 2nd element is repeated. Thus the two-body
parameters for Si interacting with C, comes from the SiCC entry. By
symmetry, the twobody parameters in the SiCC and CSiSi entries should
thus be the same. The parameters used for a particular three-body
interaction come from the entry with the corresponding three elements.
The parameters used only for two-body interactions
(n, beta, lambda2, B, lambda1, and A)
in entries whose 2nd and 3rd element are different (e.g. SiCSi)
are not used for anything and can be set to 0.0 if desired.
general, be the same. The parameters used for the two-body
interaction come from the entry where the 2nd element is repeated.
Thus the two-body parameters for Si interacting with C, comes from the
SiCC entry. By symmetry, the twobody parameters in the SiCC and CSiSi
entries should thus be the same. The parameters used for a particular
three-body interaction come from the entry with the corresponding
three elements. The parameters used only for two-body interactions
(n, beta, lambda2, B, lambda1, and A) in entries whose 2nd and 3rd
element are different (e.g. SiCSi) are not used for anything and can
be set to 0.0 if desired.
We chose the above form so as to enable users to define
all commonly used variants of the Tersoff potential.
In particular, our form reduces to the original
Tersoff form when m = 3 and gamma = 1, while it reduces to the form of "Albe
et al."_#Albe when beta = 1 and m = 1. Tersoff used a slightly
different but equivalent form for alloys, which we will refer to
as "Tersoff_2"_#Tersoff_2.
We chose the above form so as to enable users to define all commonly
used variants of the Tersoff potential. In particular, our form
reduces to the original Tersoff form when m = 3 and gamma = 1, while
it reduces to the form of "Albe et al."_#Albe when beta = 1 and m = 1.
Tersoff used a slightly different but equivalent form for alloys,
which we will refer to as Tersoff_2 potential
"(Tersoff_2)"_#Tersoff_2.
LAMMPS parameter values for Tersoff_2 can be obtained as follows.
The parameters for species i and j can be calculated
@ -126,23 +126,25 @@ using the Tersoff_2 mixing rules:
:c,image(Eqs/pair_tersoff_2.jpg)
Values not shown are determined by the first atom type. Finally, the
Tersoff_2 parameters R and S must be converted to the LAMMPS parameters
R and D (R is different in both forms), using the following relations:
R=(R'+S')/2 and D=(S'-R')/2, where the primes indicate the Tersoff_2 parameters.
Values not shown are determined by the first atom type. Finally, the
Tersoff_2 parameters R and S must be converted to the LAMMPS
parameters R and D (R is different in both forms), using the following
relations: R=(R'+S')/2 and D=(S'-R')/2, where the primes indicate the
Tersoff_2 parameters.
In the potentials directory, the file SiCGe.tersoff
provides the LAMMPS parameters for Tersoff's various versions of Si, as well
as his alloy paramters for Si, C, and Ge. This file can be
used for pure Si, (three different versions), pure C, pure Ge, binary SiC, and binary SiGe.
LAMMPS will generate an error
if this file is used with any combination involving C and Ge, since there are no entries for
the GeC interactions (Tersoff did not publish parameters for this cross-interaction.)
Tersoff files are also provided for the SiC alloy (SiC.tersoff) and the GaN (GaN.tersoff)
alloys.
In the potentials directory, the file SiCGe.tersoff provides the
LAMMPS parameters for Tersoff's various versions of Si, as well as his
alloy paramters for Si, C, and Ge. This file can be used for pure Si,
(three different versions), pure C, pure Ge, binary SiC, and binary
SiGe. LAMMPS will generate an error if this file is used with any
combination involving C and Ge, since there are no entries for the GeC
interactions (Tersoff did not publish parameters for this
cross-interaction.) Tersoff files are also provided for the SiC alloy
(SiC.tersoff) and the GaN (GaN.tersoff) alloys.
Many thanks to Rutuparna Narulkar, David Farrell, and Xiaowang Zhou for helping clarify
how Tersoff parameters for alloys have been defined in various papers.
Many thanks to Rutuparna Narulkar, David Farrell, and Xiaowang Zhou
for helping clarify how Tersoff parameters for alloys have been
defined in various papers.
:line
@ -197,7 +199,10 @@ appropriate units if your simulation doesn't use "metal" units.
:link(Tersoff_1)
[(Tersoff_1)] J. Tersoff, Phys Rev B, 37, 6991 (1988).
:link(Albe)
[(Albe)] J. Nord, K. Albe, P. Erhartand K. Nordlund, J. Phys.: Condens. Matter, 15, 5649(2003).
[(Albe)] J. Nord, K. Albe, P. Erhartand K. Nordlund, J. Phys.:
Condens. Matter, 15, 5649(2003).
:link(Tersoff_2)
[(Tersoff_2)] J. Tersoff, Phys Rev B, 39, 5566 (1989)