Quantum mechanical study of the kinetics, mechanisms and thermodynamics of the gas-phase decomposition of Pb[(ⁱPr)₂PSSe]₂ single-source precursor

The reaction mechanism of the gas phase decomposition of Pb[(ⁱPr)₂PSSe]₂ single-source precursor has been investigated theoretically by means of the density functional theory (DFT). The geometries of all the stationary points and the selected points along the potential energy surfaces were optimized at the M06/LACVP∗ level of theory. The harmonic vibrational frequencies of all the stationary points were calculated at the above same level of theory. Ten possible reaction pathways including seventeen reaction pathways on both the singlet and doublet potential energy profiles were explored. The results indicate that the steps that lead to PbS formation on both the singlet and the doublet potential energy surfaces are favored kinetically over those that lead to PbSe and ternary PbSe_xS_1-x formation. However, thermodynamically, the steps that lead to ternary PbSe_xS_1-x formation are more favorable than those that lead to PbSe and PbS formation on the doublet PESs. Moreover, the energetics also suggests the proposed scheme involving the dissociation of PbSe to be the most stable species on the singlet PES. Density functional theory calculations of the gas phase decomposition of the complex indicate that the deposition of ternary PbSe_xS_1-x in chemical vapor deposition may involve more than one steps but the steps that lead to the its formation are consistent with a dominant role for thermodynamic factors, than kinetic.