Efficient calculation of isotropic hyperfine constants of phosphorus radicals using density functional theory

Calculations of the isotropic hyperfine coupling constants of phosphorus nuclei in different environments have been carried out using density functional theory with both B3LYP and B3PW91 functionals and a variety of one-electron basis sets. A set of 35 radicals, radical cations, and tripler species containing P have been analyzed, including the set recently examined by Cramer and Lim (J. Phys. Chem. 1994, 98, 5024) using the UMP2 method. The dependency of the calculated spin densities with respect to the methods, basis sets, and geometries have been investigated. Overall, the B3LYP method, in conjunction with a TZVP basis optimized for DFT calculations and further augmented by right 1s-functions on all heavy atoms, appears to be the most efficient treatment, presumably owing to better cancelations of intrinsic errors. Depending on the size of the species examined and/or the spin contamination of UHF references, use of UMP2 geomelries is preferred, otherwise B3LYP/6-311G(d,p) geometries are a reasonable choice. In both cases, linear correlation between computed and observed values have been found with slopes close to unity and small intercepts less than or equal to 10 G.