Diatomic bond lengths and vibrational frequencies: assessment of recently developed exchange-correlation functionals

Bond lengths and harmonic vibrational frequencies of 45 singlet ground state diatomic molecules, drawn evenly from three rows of the periodic table (Li–Br), are determined using Kohn–Sham theory with the HCTH93, HCTH407, 1/4, PBE, B3LYP, B97-2, and PBE0 exchange-correlation functionals. The highly parameterised 1/4 functional, which depends on the density and its gradient with no orbital exchange, provides the best overall performance. The 1/4 exchange-correlation enhancement factor plot differs considerably from that of HCTH93 and HCTH407. As demanded by the uniform density scaling condition, the curves of different Wigner–Seitz radius do not cross.