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[lammps-users] How to calculate cohesive energy of an alloy
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[lammps-users] How to calculate cohesive energy of an alloy


From: Vijay Reddy <vijay00vegeta@...24...>
Date: Mon, 21 Aug 2017 00:14:46 +0530

Dear all,

I want to calculate the cohesive energy of Ni-Zr (4 at. %) alloy using lammps. But the tutorial provides calculation of cohesive energy for a single system.

I have modified it by increasing the box size (it does not change the cohesive energy) and incorporating 4 at.% Zr atoms using set command:

# Find minimum energy fcc configuration
# Mark Tschopp, 2010

# ---------- Initialize Simulation --------------------- 
clear 
units metal 
dimension 3 
boundary p p p 
atom_style atomic 
atom_modify map array

# ---------- Create Atoms --------------------- 
lattice 	fcc 4
region	box block 0 1 0 1 0 1 units lattice
create_box	1 box

lattice	fcc 4 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1  
create_atoms 1 box
replicate 1 1 1
set        region box type/fraction 2 0.04 12543796
# ---------- Define Interatomic Potential --------------------- 
pair_style eam/fs
pair_coeff * * Ni-Zr_Mendelev_2012.eam.fs Ni Zr
neighbor 2.0 bin 
neigh_modify delay 10 check yes 
 
# ---------- Define Settings --------------------- 
compute eng all pe/atom 
compute eatoms all reduce sum c_eng 

# ---------- Run Minimization --------------------- 
reset_timestep 0 
fix 1 all box/relax iso 0.0 vmax 0.001
thermo 10 
thermo_style custom step pe lx ly lz press pxx pyy pzz c_eatoms 
min_style cg 
minimize 1e-25 1e-25 5000 10000 

variable natoms equal "count(all)" 
variable teng equal "c_eatoms"
variable length equal "lx"
variable ecoh equal "v_teng/v_natoms"

print "Total energy (eV) = ${teng};"
print "Number of atoms = ${natoms};"
print "Lattice constant (Angstoms) = ${length};"
print "Cohesive energy (eV) = ${ecoh};"

print "All done!" 
Can this modification be used for calculation of cohesive energy of Ni-Zr alloy?


--
With Thanks and Regards,

K Vijay Reddy
Metallurgical and Materials Engineering
National Institute of Technology 
Rourkela