Dear LAMMPS users

I’m using this command:

**pair_style buck 20**

**pair_coeff * * 2442.60 0.3054 17.51**

**cut off= 20A**

**A= 2442.60 A**

**rho= 0.3054 eV**

**C= 17.51 eV A^6**

but there is an error saying that these parameters are out of bound. Can anybody help me with this problem. Whats wrong with this command.

Regards

Afza Shahid

Please put the input script lines and the error message in your mail post.

Steve

Dear Steve

I have run the simulation using arbitrary values for coefficients of buckingham potential and there is no error but when I give the actual values of coefficients of Buckingham potential there an error saying All pair coeff are not set. Input script is given below:

# ---------- Initialize Simulation ---------------------

clear

units metal

dimension 3

boundary p p p

atom_style atomic

atom_modify map array

# ---------- Create Atoms ---------------------

read_data YzOO.in

#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

mass 1 88.90

mass 2 91.22

mass 3 16.0

#replicate 1 1 1

# ---------- Define Interatomic Potential ---------------------

**pair_style buck 2.5**

**pair_coeff 1 3 2442.60 0.3054 17.51 #Y-O interaction**

**pair_coeff 2 3 1402.57 0.3312 5.10 #Zr-O interaction**

**pair_coeff 3 3 35686.18 0.2010 32.00 #O-O interaction**

neighbor 2.0 bin

neigh_modify every 1 delay 0 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!”

I have run the simulation with the pair coeff command given below (**supposed values for coefficients**) and it shows no error.

**pair_style buck 2.5**

**pair_coeff * * 100.0 1.5 200.0**

Kindly help me where exactly the problem is.

Regards

Afza Shahid.

Please put the input script lines and the error message in your mail post.

Steve

Dear Steve

I have run the simulation using arbitrary values for coefficients of

buckingham potential and there is no error but when I give the actual

values of coefficients of Buckingham potential there an error saying All

pair coeff are not set. Input script is given below:

that error message is self-explanatory! you are not providing pair_coeff

entries for all pairs of atom types. where are the parameters for Y-Y,

Y-Zr, and Zr-Zr interactions?

if you use pair_coeff * *, you implicitly assign parameters of all pairs of

types.

also, your global non-bonded cutoff of 2.5 angstrom does not make any sense

for a system with metal units. it *must* be wrong.

axel.