Transition probabilities for the Au (S2, D2, and P2) with SiH4 reaction

Abstract

Transition probabilities on the interaction of the ground and the lowest excited states of gold Au ((2)S:5d(10)6s(1), (2)D:5d(9)6s(2), and (2)P:5d(10)6p(1)) with silane (SiH(4)) are studied through ab initio Hartree-Fock self-consistent field calculations, where the atom's core is represented by relativistic effective core potentials. These calculations are followed by a multiconfigurational self-consistent field study. The correlation energy is accounted for through extensive variational and perturbative second order multireference Moller-Plesset configuration interaction analysis of selected perturbations obtained by iterative process calculations using the CIPSI program package. It is found that the Au atom in the ((2)P:5d(10)6p(1)) state inserts in the Si-H bond. In this interaction its corresponding D (2)A(') potential energy surface is initially attractive and only becomes repulsive after encountering an avoided crossing with the initially repulsive C (2)A(') surface linked to the Au((2)D:5d(9)6s(2))-SiH(4) fragments. The A, B, and C (2)A(') curves derived from the Au((2)D:5d(9)6s(2)) atom interaction with silane are initially repulsive, each one of them showing two avoided crossings, while the A (2)A(') curve goes sharply downwards until it meets the X (2)A(') curve interacting adiabatically, which is linked with the Au((2)S:5d(10)6s(1))-SiH(4) moieties. The A (2)A(') curve becomes repulsive after the avoided crossing with the X (2)A('), curve. The lowest-lying X (2)A(') potential leads to the HAuSiH(3) X (2)A(') intermediate molecule. This intermediate molecule, diabatically correlated with the Au((2)P:5d(10)6p(1))+SiH(4) system which lies 3.34 kcal/mol above the ground state reactants, has been carefully characterized as have the dissociation channels leading to the AuH+SiH(3) and H+AuSiH(3) products. These products are reached from the HAuSiH(3) intermediate without any activation barrier. The Au-SiH(4) calculation results are successfully compared to experiment. Landau-Zener theory of avoided crossings is applied to these interactions considering the angle theta instead of the distance r as the reaction coordinate.

Potential Energy Surfaces for Reactions of X Metal Atoms (X = Cu, Zn, Cd, Ga, Al, Au, or Hg) with YH4 Molecules (Y = C, Si, or Ge) and Transition Probabilities at Avoided Crossings in Some Cases

“…In any case, our reported energies are compatible with the spectra of reactants, intermediates, and products. For instance, the probabilities for the Ga + CH 4 reaction agree quite well with experimental results [83,96], whereas those obtained for other systems reported here were widely discussed in the original papers [82][83][84][85][86][87][88]. The potential energy surfaces for the coinage metals Cu and Au with silane are rather similar.…”

“…Pacheco-Sánchez et al [87] have found that Gold in its second excited state ( 2 P: 5d 10 6p 1 ), through a series Taking it to pass the avoided crossing, it has a probability P = 0.802 [87] for crossing towards C 2 A maintaining the 6p 1 character, where it finds another avoided crossing, and there is a probability of 0.737 for crossing toward B 2 A also maintaining the 6p 1 character. Here it finds another avoided crossing, and there is a probability of 0.803 of crossing toward the A 2 A still maintaining the 6p 1 character (see Figure 4).…”

“…Transition probability theory is described here when the reaction parameter is distance or angle. In addition, our group has considered also the following interactions: cadmium methane [86], zinc silane [9], cadmium silane [10], mercury silane [9], gold silane [87], and recently aluminum methane [88].…”