Ab initio studies of the reactions of M(1S,3P, and 1P) with GeH4 (M=Cd, Hg)

Abstract

Ab initio studies of the reactions of Cu ( 2 S, 2 D, and 2 P) with SiH 4 and GeH 4The interaction of Cd( 1 S:5s 2 , 3,1 P:5s 1 5p 1 ) and Hg( 1 S:6s 2 , 1,3 P:6s 1 6 p 1 ) with GeH 4 were studied by means of Hartree-Fock self-consistent field ͑SCF͒ and multiconfigurational SCF plus variational and multireference second order Möller-Plesset perturbational configuration interaction ͑CIPSI͒ calculations, using relativistic effective core potentials. It was found that both metal atoms in their 3 P(ns 1 np 1 ) state break spontaneously the Ge-H bond of the germane molecule, giving place to the MHϩGeH 3 (MϭCd, Hg) final products. For both atoms, the 1 P(ns 1 np 1 ) state is also inserted in the Ge-H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X 1 AЈ potential surface adiabatically linked with the M( 1 S:ns 2 )ϩGeH 4 . This interaction leads eventually to the MHϩGeH 3 products. The HMGeH 3 X 1 A 1 (MϭCd, Hg) intermediate molecules, diabatically correlated with the M( 1 P:ns 1 np 1 )ϩGeH 4 , which lie 13.6 and 21 kcal/mol, respectively, above the ground state reactants, have been carefully characterized as well as the dissociation channels leading to the MHϩGeH 3 and HϩMGeH 3 products. These products are reached from the HMGeH 3 intermediates without activation barriers. Accurate energy differences for all these species are reported. This work suggests that the simultaneous photoexcitation of Cd and Hg atoms in the presence of silane and germane molecules in the gas phase could be used to produce better quality a-SiGe:H thin films.

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

“…This behavior is similar to the HCuSiH 3 intermediate product formation in the Cu+ CH 4 and Cu + SiH 4 interactions previously studied. This state is found to be responsible for the Si-H bond activation of the SiH 4 molecule and also the relaxation involved in the C s HAuSiH 3 intermediate product formation.…”

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

“…Luna-García et al [11] have found that mercury in its excited state ( 1 P: 5d 10 6s 1 6p 1 ) breaks the Ge-H bond of germane, while forming a ground state barrier of 86.1 kcal mol −1 . The experimental transition energy between the excited state ( 1 P: 5d 10 6s 1 6p 1 ) and the ground state ( 1 S: 5d 10 6s 2 ) amounts to 154.6 kcal mol −1 , in good agreement with the transition energy of 157.6 kcal mol −1 theoretically calculated (Table 2(c)).…”

“…Transition probabilities for the interaction of the lowest excited states of the metal X with tetrahedral gas molecules are studied through one-dimensional Landau-Zener theory. The strategy for obtaining the reaction pathways for X + YH 4 interactions has been extensively used in references [8][9][10][11][12][13][14] based on the original proposal by Chaquin et al [15]. The initial approach (starting from 20 a.u.)…”

“…Castillo et al [8,60,80] carried out calculations of potential energy surfaces of the interactions copper methane and zinc methane with the aim of determining the mechanisms of reaction that involve the three lowest states of the copper atom ( 2 S, 2 D, and 2 P) as well as to determine the reaction routes that govern the interaction of the three lowest states of the zinc atom ( 1 S, 3 P, and 1 P) in the process of the C-H bond activation of the methane molecule. Luna-García et al [11,12,81] found the interaction potential curves of the mercury-Germane, cadmium-Germane, copper-silane, and copper-germane in the three lowest states of each metal; he improved a computational methodology to get the products of the breaking of the intermediate. Pacheco-Sánchez et al [13,14,40] achieved the calculation of gallium-methane and gallium-silane interactions as much in the ground state as in the two lowest excited states of gallium; he extended Landau-Zener theory [82][83][84][85] to use the angle instead of the distance as reaction parameter in transition probability calculations at avoided crossings.…”