Some theoretical studies on hydrogen molecule capture by platinum atoms

Pseudopotential SCF‐LCAO‐MO and variational and perturbative Cl calculations were carried out for H 2 molecule capture by a single Pt atom with C 2v symmetry. A pseudopotential for the platinum atom including relativistic effects was used. Singlet and triplet states of the Pt‐H 2 interaction having different representations of the mentioned C 2v symmetry were studied. The triplet ground state of Pt leads to two A 1 and B 2 states in which the metal atom cannot capture H 2 ; i.e., both have repulsive interaction energies. The electronic state responsible for the capture of H 2 is the closed‐shell, singlet A 1 excited state. The equilibrium geometry of the system is reached with a broken HH bond at a HPtH angle of about 100°. Additionally another shallower minimum for a singlet A 1 linear structure is observed. Specific predictions for the thermal and photochemical Pt + H 2 reactions that can be carried out under matrix isolation conditions are made.