The electronic and molecular structures of Ca3P2 and Ca6P4 are investigated using high-level ab initio methods. The lowest energy structure for Ca3P2 is found to be a Jahn-Teller distorted triplet. An excited-state singlet is found with various post HF methods; however, DFT incorrectly predicts a closed shell singlet to be the ground state. For the Ca6P4 system, both DFT and ab initio methods give consistent relative energies. The computational results demonstrate that the energetics are very sensitive to the size of the Ca basis set. Enhancing the Ca basis sets with additional s and p valence functions significantly affects the calculated energies.