To determine energy trends when considering different crystal structures of a solid, it is necessary to establish the corresponding equations of state (EOS). It is important to note that one cannot rely only on the quantities obtained from lattice optimizations alone, especially when comparing the energies and volumes of different phases. The underlying physics means that the calculated total energy corresponds to the cohesion within the crystal, and the solutions to the Kohn-Sham DFT equation give the energy in terms of infinitely separated electrons and nuclei.