Hello Steve Sir,

Using the different unit cell i able to solve that.

But the lattice primitive vectors collinear is not solved. As you suggested to follow this:

variable a equal 1/sqrt(2)

lattice custom 1 a1 a a 0.0 a2 -a a 0.0 a3 0 0 1 basis 0 0 0 basis 0.0 0.5 0.5

Then also there is the same problem.

Thanking you

apurba

You need this:

variable a equal 1/sqrt(2)

variable nega equal -1/sqrt(2)

lattice custom 1 a1 $a a 0\.0 a2 {nega} $a 0.0 a3 0 0 1 &

basis 0 0 0 basis 0.0 0.5 0.5

Steve