Zener ratio

The Zener ratio is a dimensionless number that is used to quantify the anisotropy for cubic crystals. It is sometimes referred as anisotropy ratio and is named after Clarence Zener. Conceptually, it quantifies how far a material is from being isotropic (where the value of 1 means an isotropic material).

Its mathematical definition is

${\displaystyle a_{r}={\frac {2C_{44}}{C_{11}-C_{12}}},}$

where ${\displaystyle C_{ij}}$ refers to Elastic constants in Voigt notation.