[lammps-users] HCP structure in lammps ???????

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1

Dear Steve,

the no. of atoms in HCP unit cell i.e. “N” should be “6” instead of “4” given in the manual.

N= (N_C/6)+(N_F/2)+(N_I/1)

where
N_C = total number of corner atoms in a unit cell = 6+6 = 12
N_F= total number of face atoms in a unit cell =1+1 =2
N_I= total no of interior/center atoms in a unit cell = 1+1+1 =3

hence,

N =(12/6)+(2/2)+(3/1) =6 atoms

I also tried to visualize the structure also. I am not able to see a hcp lattice.

Any suggestions?

warm regards
Vijay

2

I think 4 is correct, at least for the rectilinear unit cell LAMMPS defines
for hcp. From the lattice doc page and the code:

Style {hcp} has a1 = 1 0 0, a2 = 0
sqrt(3) 0, and a3 = 0 0 sqrt(8/3). A {hcp} lattice has 4 basis
atoms, two in the z = 0 plane and 2 in the z = 0.5 plane.

} else if (style == HCP) {
add_basis(0.0,0.0,0.0);
add_basis(0.5,0.5,0.0);
add_basis(0.5,5.0/6.0,0.5);
add_basis(0.0,1.0/3.0,0.5);

Steve