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revise the doc of Tersoff potential accordingly

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Wengen Ouyang
2020-12-24 16:45:22 +02:00
parent 7b4d4e41b8
commit 9b6ba42c19
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doc/src/pair_tersoff.rst
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@ -26,10 +26,15 @@ Syntax
.. code-block:: LAMMPS
pair_style style delta
pair_style style keywords values
* style = *tersoff* or *tersoff/table* or *tersoff/shift* or *tersoff/gpu* or *tersoff/omp* or *tersoff/table/omp*
* delta = the shift applied to the equilibrium bond length of the tersoff potential (for tersoff/shift only).
* keyword = *shift*
.. parsed-literal::
*shift* value = delta
delta = the value of the shift applied to the equilibrium bond length of the tersoff potential
Examples
""""""""
@ -43,7 +48,7 @@ Examples
pair_style tersoff/table
pair_coeff * * SiCGe.tersoff Si(D)
pair_style tersoff/shift 0.05
pair_style tersoff shift 0.05
pair_coeff * * Si.tersoff Si
Description
@ -73,7 +78,7 @@ The *tersoff* style computes a 3-body Tersoff potential
where :math:`f_R` is a two-body term and :math:`f_A` includes three-body
interactions. The summations in the formula are over all neighbors
J and K of atom I within a cutoff distance = R + D. math:`\delta` is
non-zero only for *tersoff/shift* style.
the shift applied to the equilibrium bond length.
The *tersoff/table* style uses tabulated forms for the two-body,
environment and angular functions. Linear interpolation is performed
@ -81,7 +86,7 @@ between adjacent table entries. The table length is chosen to be
accurate within 10\^-6 with respect to the *tersoff* style energy.
The *tersoff/table* should give better performance in terms of speed.
The *tersoff/shift* style computes the energy E of a system of atoms, whose formula
The *shift* keyword computes the energy E of a system of atoms, whose formula
is the same as the Tersoff potential. The only modification is that the original
equilibrium bond length (:math: `r_0`) of the system is shifted to :math:`r_0-\delta`.
@ -91,7 +96,7 @@ equilibrium bond length (:math: `r_0`) of the system is shifted to :math:`r_0-\d
or shrinked relative to the original value. Specifically, values of :math:`\delta < 0` will result in
elongation of the bond length, while values of :math:`\delta > 0` will result in shrinking of the bond length.
This *tersoff/shift* style is designed for simulations of closely matched van der Waals heterostructures.
This *shift* keyword is designed for simulations of closely matched van der Waals heterostructures.
For instance, let's consider the case of a system with few-layers graphene atop a thick hexagonal boron nitride (h-BN)
substrate simulated using periodic boundary conditions. The experimental lattice mismatch of ~1.8% between graphene
and h-BN is not well captured by the equilibrium lattice constants of available potentials, thus a small in-plane strain
@ -104,7 +109,7 @@ For the specific case discussed above, the force field can be defined as
.. code-block:: LAMMPS
pair_style hybrid/overlay rebo tersoff/shift -4.07e-3 ilp/graphene/hbn 16.0 coul/shield 16.0
pair_style hybrid/overlay rebo tersoff shift -4.07e-3 ilp/graphene/hbn 16.0 coul/shield 16.0
pair_coeff * * rebo CH.rebo NULL NULL C
pair_coeff * * tersoff/shift BNC.tersoff B N NULL
pair_coeff * * ilp/graphene/hbn BNCH.ILP B N C