Building up a triangular lattice

A triangular lattice

The triangular lattice is sometimes called hexagonal lattice, which may cause some confusion. It can be viewed as a skewed rectangular lattice. It surface density is

$\rho \sigma ^{2}={\frac {2}{\sqrt {3}}},$

where $\sigma$ is the distance between nodes of the lattice. The dual of this lattice is the honeycomb lattice.

References

Triangular lattice entry in wikipedia