Ab initio studies of the reactions of Cu(2S, 2D, and 2P) with SiH4 and GeH4

Abstract

The interactions of Cu(2S:3d104s1, 2D:3d94s2, and 2P:3d104p1) with SiH4 and GeH4 were studied by means of Hartree–Fock–SCF and multiconfigurational-SCF followed by variational and multireference second order Möller–Plesset perturbational configuration interaction (CIPSI) calculations, using relativistic effective core potentials. The Cu atom in its P2(3d104p1) state is inserted in the Si–H and Ge–H bonds. In both interactions their corresponding 5 2A′ potential energy surfaces are initially attractive and become repulsive only after having encountered the avoided crossing region with the initially repulsive 4 2A′ surface adiabatically linked with the Cu(2D:3d94s2)–SiH4(GeH4) fragments. The three A′2 curves derived from the interaction of the Cu(2D:3d94s2) atom with silicon (or germane) molecule are initially repulsive. Each one of them shows two avoided crossings and its lowest lying 2 2A′ curve goes sharply down until it meets the X 2A′ curve adiabatically linked with the Cu(2S:3d104s1)+SiH4(GeH4) asymptotes. The 2 2A′ curve becomes repulsive after the avoided crossing with the X 2A′ curve. The lowest-lying X 2A′ potential leads to the HCuZH3 X 2A1 (Z=Si, Ge) intermediate molecule. This intermediate molecule, diabatically correlated with the Cu(2P:3d104p1)+ZH4 fragments which lie 5.8 and 1.6 kcal/mol, respectively, above the ground state reactants, have been carefully characterized as well as the dissociation channels leading to the CuH+ZH3 and H+CuZH3 products. These products are reached from the HCuZH3 intermediates without activation barriers. This work suggests that the simultaneous photoexcitation of the Cu atom in 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

“…5 For Au, the first avoided crossing takes place for a ͑H-Au-Si͒ insertion angle of 28°and the C 2 AЈ surface presents an activation barrier of nearly 37 kcal/mol. 5 For Au, the first avoided crossing takes place for a ͑H-Au-Si͒ insertion angle of 28°and the C 2 AЈ surface presents an activation barrier of nearly 37 kcal/mol.…”

“…The transition state geometrical parameters are given in Table I. 5 In Fig. In this last case, the avoided crossing takes place at a ͑H-Cu-Si͒ insertion angle of 50°and the lowest-lying surface presents an activation barrier of 26 kcal/mol.…”

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

“…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.…”

The Induced Electrochemical Codeposition of Cu-Ge Alloy Films

“…According to ab initio studies and Hartree-Fock self-consistentfield calculations performed in vacuum conditions 19,20 photoexcited Cu atoms would spontaneously activate the Ge-H bond without any activation barrier, forming intermediate species of the form H-CuGe-H 3 , which may dissociate in CuH + GeH 3 or H + CuGeH 3 . We hypothesize that a similar mechanism is active in aqueous solutions in the potential range starting at and more negative than −1.5 V, where the Cu ion during the charge transfer process would likely be in an excited state, while H could easily dissociate from the compound, likely releasing H ad species, and possibly leading to the formation of a Cu-Ge bond.…”