\(\renewcommand{\AA}{\text{Å}}\)
pair_style smatb command
pair_style smatb/single command
Syntax
pair_style style args
style = smatb or smatb/single
args = none
Examples
pair_style smatb
pair_coeff 1 1 2.88 10.35 4.178 0.210 1.818 4.07293506 4.9883063257983666
pair_style smatb/single
pair_coeff 1 1 2.88 10.35 4.178 0.210 1.818 4.07293506 4.9883063257983666
Description
Added in version 4May2022.
The smatb and smatb/single styles compute the Second Moment Approximation to the Tight Binding (Cyrot), (Gupta), (Rosato), given by
\(R_{ij}\) is the distance between the atom \(i\) and \(j\). And the two functions \(\alpha\left(r\right)\) and \(\Xi\left(r\right)\) are:
The polynomial coefficients \(a_3\), \(a_4\), \(a_5\), \(x_3\), \(x_4\), \(x_5\) are computed by LAMMPS: the two exponential terms and their first and second derivatives are smoothly reduced to zero, from the inner cutoff \(R_{sc}\) to the outer cutoff \(R_{c}\).
The smatb/single style is an optimization when using only a single atom type.
Coefficients
The following coefficients must be defined for each pair of atoms types via the pair_coeff command as in the examples above, or in the data file or restart files read by the read_data or read_restart commands, or by mixing as described below:
\(R_{0}\) (distance units)
\(p\) (dimensionless)
\(q\) (dimensionless)
\(A\) (energy units)
\(\xi\) (energy units)
\(R_{cs}\) (distance units)
\(R_{c}\) (distance units)
Note that: \(R_{0}\) is the nearest neighbor distance, usually coincides with the diameter of the atoms
See the run_style command for details.
Mixing info
For atom type pairs I,J and I != J the coefficients are not automatically mixed.
Restrictions
These pair styles are part of the SMTBQ package and are only enabled if LAMMPS is built with that package. See the Build package page for more info.
These pair styles require the newton setting to be “on” for pair interactions.
Default
none
(Cyrot) Cyrot-Lackmann and Ducastelle, Phys Rev. B, 4, 2406-2412 (1971).
(Gupta) Gupta ,Phys Rev. B, 23, 6265-6270 (1981).
(Rosato) Rosato and Guillope and Legrand, Philosophical Magazine A, 59.2, 321-336 (1989).