The authors have calculated the total energy and equilibrium volumes of La₂CuO₄ and La_1.5Sr_0.5CuO₄ using the local density approximation to density functional theory (DFT). The calculations were performed using the ASA LMTO method under the constraint of a fixed c/a ratio. The calculated equilibrium volumes are in good agreement with experiment indicating that DFT provides a useful starting point for a discussion of the energetics of this class of superconductor. In the strontium compound they find local charge redistributions that result in holes in the p band of the out-of-plane oxygen atoms. These local charge rearrangements invalidate the use of the rigid band and virtual crystal models for describing alloying.