The linear elasticity theory reviewed in Chapter 2 is applied here for the calculation of the dislocation energy within an isotropic (Section 3.3) and anisotropic (Section 3.4) framework. Both treatments are applied to calculate the pre-logarithmic coefficients (see Sections 3.5 and 3.6), both of which are important parameters used to evaluate the geometrical configurations of dislocations inside AlN, GaN and InN (Section 3.7). The importance of the dislocation configuration is made evident in the modeling of the dislocation density, as described in Chapter 5.