lammps/examples/UNITS/in.ar.metal

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Metal
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2019-10-09 08:02:21 +08:00
# Ar in metal units
# simulation params in reduced units
# settable from command line
# epsilon, sigma, mass set below
variable x index 5
variable y index 5
variable z index 5
variable rhostar index 0.8842
variable dt index 0.005
variable cutoff index 2.5
variable skin index 0.3
variable tinitial index 1.0
variable nthermo index 10
variable nsteps index 100
# physical constants from update.cpp
variable kb index 8.617343e-5 # kB in eV/K
variable avogadro index 6.02214129e23 # Avogadro's number
# Ar properties in metal units
variable epskb index 117.7 # LJ epsilon/kB in degrees K
variable sigma index 3.504 # LJ sigma in Angstroms
variable epsilon equal ${epskb}*${kb} # LJ epsilon in eV
variable mass index 39.95 # mass in g/mole
# scale factors
# sigma = scale factor on distance, converts reduced distance to Angs
# epsilon = scale factor on energy, converts reduced energy to eV
# tmpscale = scale factor on temperature, converts reduced temp to degrees K
# tscale = scale factor on time, converts reduced time to ps
# formula is t = t* / sqrt(epsilon/mass/sigma^2), but need t in fs
# use epsilon (Joule), mass (kg/atom), sigma (meter) to get t in seconds
# pscale = scale factor on pressure, converts reduced pressure to bars
# formula is P = P* / (sigma^3/epsilon), but need P in atmospheres
# use sigma (meter), epsilon (Joule) to get P in nt/meter^2, convert to bars
variable eVtoJoule index 1.602e-19 # convert eV to Joules
variable NtMtoAtm equal 1.0e-5 # convert Nt/meter^2 to bars
variable tmpscale equal ${epskb}
variable epsilonJ equal ${epsilon}*${eVtoJoule}
variable massKgAtom equal ${mass}/1000.0/${avogadro}
variable sigmaM equal ${sigma}/1.0e10
variable sigmaMsq equal ${sigmaM}*${sigmaM}
variable tscale equal 1.0e12/sqrt(${epsilonJ}/${massKgAtom}/${sigmaMsq})
variable sigmaM3 equal ${sigmaM}*${sigmaM}*${sigmaM}
variable pscale equal ${NtMtoAtm}/(${sigmaM3}/(${epsilonJ}))
# variables
# alat = lattice constant in Angs (at reduced density rhostar)
# temp = reduced temperature for output
# epair,emol,etotal = reduced epair,emol,etotal energies for output
# press = reduced pressure for output
variable alat equal (4.0*${sigma}*${sigma}*${sigma}/${rhostar})^(1.0/3.0)
variable temp equal temp/${tmpscale}
variable epair equal epair/${epsilon}
variable emol equal emol/${epsilon}
variable etotal equal etotal/${epsilon}
variable press equal press/${pscale}
# same script as in.ar.lj
units metal
atom_style atomic
lattice fcc ${alat}
region box block 0 $x 0 $y 0 $z
create_box 1 box
create_atoms 1 box
mass 1 ${mass}
velocity all create $(v_tinitial*v_epskb) 12345
pair_style lj/cut $(v_cutoff*v_sigma)
pair_coeff 1 1 ${epsilon} ${sigma}
neighbor $(v_skin*v_sigma) bin
neigh_modify delay 0 every 20 check no
fix 1 all nve
timestep $(v_dt*v_tscale)
# columns 2,3,4 = temp,pe,press in metal units
# columns 5-9 = temp,energy.press in reduced units, compare to in.ar.lj
# need to include metal unit output to enable use of reduced variables
thermo_style custom step temp pe press v_temp v_epair v_emol v_etotal v_press
thermo_modify norm yes
thermo ${nthermo}
run ${nsteps}