W4 thermochemistry of P-2 and P-4. 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 P-2 and P-4 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 Delta H degrees(f),(0)[P(g)] = 75.54 +/- 0.1 kcal mol(-1) and Delta H degrees(f),(298) [P(g)] = 75.74 +/- 0.1 kcal mol(-1), in the upper half of the CODATA uncertainty interval.