Using the (C1) 4 (C2) 4 template (Table ), the crb binary compounds BX were designed and structurally optimized to the ground state energy following successive calculations with increasing precision of the k-space mesh. The results presented in Table show trends of increasing volume with X, which can be explained by the increase of the atomic radius along the 5A column: r(N) = 0.75 Å, r(P) = 1.10 Å, r(As) = 1.20 Å, r(Sb) = 1.40 Å, and r(Bi) = 1.50 Å. Note that r(B) = 0.83 Å.