The elastic stiffness tensor is of fourth order and contains () elements. Introducing additional symmetry considerations, the number of needed components can be reduced [162]. Cubic semiconductors like , or are characterized by only three constants ( ).

If the strain, instead of stress, is the quantity of interest, it can be calculated by inversion of the elastic stiffness tensor (3.10)

(3.12) |

or in matrix form

The stiffness constants are normally denoted as , while the compliance constants are named as . The compliance constants can be calculated from the stiffness constants with the following relations:

T. Windbacher: Engineering Gate Stacks for Field-Effect Transistors