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lammps/tools/moltemplate/examples/silly/pyramids_vs_gravity/moltemplate_files/graphene.lt
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# This file contains a unit cell for building graphene and nanotubes
#
#
# The 4AtomRectCellXY "molecule" defined below is a reactangular unit cell
# for hexagonal tesselations in 2-dimensions. (See "graphene_unit_cell.jpg")
# Surfaces constructed with this unit cell can be flat or curved into tubes.
# The distance between nearest-neighbor carbon atoms (ie the length of a
# carbon-carbon bond) is equal to "d" which I set to 1.42 Angstroms.
#
# d = length of each hexagon's side = 1.42 Angstroms
# L = length of each hexagon = 2*d = 2.84 Angstroms
# W = width of each hexagon = 2*d*sqrt(3)/2 = 2.4595121467478056 Angstroms
# 2w = width of hexagon rows = 3*l = 4.26 Angstroms
#
# Consequently, the Lattice-cell vectors for singe-layer graphene are:
# (2.4595121467478, 0, 0) (aligned with X axis)
# (0, 4.26, 0) (aligned with Y axis)
# So, to build a sheet of graphite, you could use:
# sheet = new Graphene/4AtomRectCellXY [10].move(2.4595121467478, 0, 0)
# [10].move(0, 4.26, 0)
Graphene {
4AtomRectCellXY
{
# atomID molID atomType charge x y z
write("Data Atoms") {
$atom:C11 $mol:... @atom:../C 0.0 0.61487803668695 0.71 0.0
$atom:C21 $mol:... @atom:../C 0.0 1.84463411006085 1.42 0.0
$atom:C12 $mol:... @atom:../C 0.0 0.61487803668695 3.55 0.0
$atom:C22 $mol:... @atom:../C 0.0 1.84463411006085 2.84 0.0
}
}
# Now define properties of the Carbon graphene atom
write_once("In Init") {
pair_style hybrid lj/cut 9.0
}
write_once("Data Masses") {
@atom:C 12.0
}
write_once("In Settings") {
# i j epsilon sigma
pair_coeff @atom:C @atom:C lj/cut 0.068443 3.407
# These Lennard-Jones parameters come from
# R. Saito, R. Matsuo, T. Kimura, G. Dresselhaus, M.S. Dresselhaus,
# Chem Phys Lett, 348:187 (2001)
# Define a group consisting of only carbon atoms in graphene molecules
group gGraphene type @atom:C
}
} # Graphene
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