From 5472c92086d5d57b081517d76c64eec267f38443 Mon Sep 17 00:00:00 2001 From: sjplimp Date: Thu, 25 Oct 2007 16:52:37 +0000 Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@1099 f3b2605a-c512-4ea7-a41b-209d697bcdaa --- doc/pair_tersoff.html | 81 +++++++++++++++++++++++-------------------- doc/pair_tersoff.txt | 75 ++++++++++++++++++++------------------- 2 files changed, 83 insertions(+), 73 deletions(-) diff --git a/doc/pair_tersoff.html b/doc/pair_tersoff.html index 68af7aa633..d2cd3e7f0a 100644 --- a/doc/pair_tersoff.html +++ b/doc/pair_tersoff.html @@ -23,8 +23,8 @@ pair_coeff * * SiC.tersoff Si C Si

Description:

-

The tersoff style computes a 3-body Tersoff potential -for the energy E of a system of atoms as +

The tersoff style computes a 3-body Tersoff potential +(Tersoff_1) for the energy E of a system of atoms as

@@ -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.

-

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. when beta = 1 and m = 1. Tersoff used a slightly -different but equivalent form for alloys, which we will refer to -as 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. 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).

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:

-

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.

@@ -200,11 +202,14 @@ appropriate units if your simulation doesn't use "metal" units. -(Tersoff_1) J. Tersoff, Phys Rev B, 37, 6991 (1988). - - -(Albe) J. Nord, K. Albe, P. Erhartand K. Nordlund, J. Phys.: Condens. Matter, 15, 5649(2003). +

(Tersoff_1) J. Tersoff, Phys Rev B, 37, 6991 (1988). +

+ +

(Albe) J. Nord, K. Albe, P. Erhartand K. Nordlund, J. Phys.: +Condens. Matter, 15, 5649(2003). +

+

(Tersoff_2) J. Tersoff, Phys Rev B, 39, 5566 (1989)

diff --git a/doc/pair_tersoff.txt b/doc/pair_tersoff.txt index 3c3c9a0a09..25612c4e1a 100644 --- a/doc/pair_tersoff.txt +++ b/doc/pair_tersoff.txt @@ -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)