However, single point energies obtained from QM calculation usually have charges separated at infinity and T = 0 K as the zero of energy. Figure shows how this difference in the zero of energy can be resolved to calculate the desired heats of formation ∆H f (M, 298 K). To emphasize the conceptual meaning for each leg of the cycle, we have left out stoichiometric coefficients that serve to balance the number of each type of element for each step to avoid cluttering the figure. On the left-hand side of Figure , we have the desired quantity, ∆H f (M, 298 K), and on the bottom right corner, we have the above-mentioned QM zero of energy. The corrections for temperature effects on enthalpies are simply related by heat capacitiy integrals, and the complexity lies on the calculation of ∆H f (M, 0 K) from QM results. Applying Equation 1 for 0 K reveals that the needed quantities are H f (CH 4 , 0 K), H f (C, graphite, 0 K), and H f (H 2 , 0 K).