The electronic structure of the PtH molecule: Fully relativistic configuration interaction calculations of the ground and excited states

Fully relativistic all‐electron self‐consistent field calculations based on the Dirac–Coulomb Hamiltonian have been performed on the three lowest lying states of the PtH molecule. The resulting four‐component Dirac–Hartree–Fock (DHF) molecular spinors are subsequently used in relativistic configuration interaction (CI) calculations on the five lower states of PtH. Spectroscopic properties are obtained by fitting the potential curve to a Morse function and show good agreement with experimental data. The effect of relativistic corrections to the Coulomb electron–electron interaction is investigated at the DHF level and is found to be insignificant for the molecular spectroscopic properties investigated by us. The CI wave functions are found to have only one dominant configuration, indicating a lack of static correlation. Dynamic correlation in the d shell is, however, important for the spectroscopic properties of PtH. The results conform with a bonding scheme in which the three lower and two upper states of PtH are assigned 5d3/245d5/25σ1/22 and 5d3/235d5/26σ1/22 electronic configurations, respectively. The configurations are only approximate and are perturbed by 5d participation in bonding. The stability of the Pt–H bond is explained in terms of the relativistic stabilization of the 6s orbital in analogy with the electron affinity of the platinum atom.