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W4 thermochemistry of P2 and P4. Is the CODATA heat of formation of the phosphorus atom correct?

The high-accuracy W4 computational thermochemistry protocol, and several post-W4 methods, have been applied to the P2 and P4 molecules. Contrary to previous studies, we find the experimental thermochemistry to be fundamentally sound. The reaction enthalpy for P4→2P 2 has a very significant contribution from post-CCSD(T) correlation effects. We derive a gas-phase heat of formation for the phosphorus atom of  kcal mol−1 and  kcal mol−1, in the upper half of the CODATA uncertainty interval.