Contraction of the well-tempered Gaussian basis sets: The first-row diatomic molecules

The well‐tempered Gaussian basis sets (14s 10p) for atoms from lithium to neon were contracted and used in restricted Hartree–Fock calculations on 13 systems: Li2(Σ), B2(Σ), C2(Σ), N2(Σ), O2(Σ), F2(Σ), Ne2(Σ), LiF(Σ), BeO(Σ), BF(Σ), CN−(Σ), CO(Σ), and NO+(Σ). Spectroscopic constants (Re, ωe, ωexe, Be, αe, and ke) and one‐electron properties (dipole, quadrupole, and octupole moments at the center of mass and electric field, electric field gradient, potential, and electron density at the nuclei) were evaluated and compared with the Hartree–Fock results. The largest contracted basis set (7s6p3d) gives results very close to the Hartree–Fock values; the remaining differences are attributed to the absence of the f functions in the present basis sets. For Ne2, the interaction energy was calculated; the magnitude of the basis‐set superposition error was found to be very small (less than 3 μEh at 2.8 a0 and less than 2 μEh at 5.0 a0).