Hello all,

I am simulating Be system of particles whose lattice is described below(HCP). Z-dimension is kept in periodic. As a rule if any dimension is in periodicity, it should be defined in such a way that it should be in integral multiple of the lattice constant in that dimension. I used a multiple of **‘variable c’** (18.134 nm) but atoms are getting unstable. I want to know which variable multiple should be used for z-dimension to be periodic.

**variable a equal 2.2568**

**variable b equal $a*sqrt(3.0)**

**variable c equal $a*1.5682**

**lattice custom 1.0 a1 $a 0.0 0.0 &**

**a2 0.0 $b 0.0 &**

**a3 0.0 0.0 $c &**

**basis 0.0 0.0 0.0 &**

**basis 0.5 0.5 0.0 &**

**basis 0.0 0.33333333 0.5 &**

**basis 0.5 0.83333333 0.5**