The reactions of Zn(1S, 3P, and 1P) with SiH4 have been studied through multiconfigurational self-consistent field (with relativistic effective core potentials) followed by extensive variational and perturbational second-order multireference Möller–Plesset configuration interaction by perturbation selected by iterative process calculations using extended Gaussian basis sets. The Zn atom in the 3P(4s14p1) state breaks the Si–H bond of silane spontaneously, leading directly to the ZnH+SiH3 final products, in agreement with experimental results. The 1P(4s14p1) Zn atom is also inserted in the Si–H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X 1A′ potential surface, adiabatically correlated with the Zn(1S:4s2)+SiH4 reactants. This interaction leads also to the ZnH+SiH3 products. The structure of the HZnSiH3 intermediate product was carefully studied as well as the dissociation channels leading to the ZnH+SiH3 and H+ZnSiH3 products. Accurate energy differences between these species are also reported. The qualitative difference in the behavior of the 3P(4s14p1) Zn reaction with methane and silane has been explained by analyzing the corresponding potential energy surfaces; the present results confirm the C–H bond steric hindrance hypothesis advanced by Wang et al. [J. Chem. Phys. 104, 9401 (1996)].

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The interactions of Ga((2)P:4s(2)4p(1), (2)S:4s(2)5s(1), and (2)P:4s(2)5p(1)) with SiH(4) are studied by means of Hartree-Fock self-consistent field (SCF) and multiconfigurational SCF followed by extensive variational and perturbational second-order multireference Møller-Plesset configuration by perturbation selected by iterative process calculations, using relativistic effective core potentials. The Ga atom in its (2)P(4s(2)5p(1)) state can spontaneously insert into the SiH(4). The Ga atom in its (2)S(4s(2)5s(1)) state is inserted into the SiH(4). In this interaction the 3 (2)A(') potential energy surface initially attractive becomes repulsive after meeting the 2 (2)A(') surface linked with the Ga((2)P:4s(2)4p(1))+SiH(4) fragments. The two (2)A(') curves (2 (2)A(') and X (2)A(')) derived from the interaction of Ga((2)P:4s(2)4p(1)) atom with silane molecule are initially repulsive. The 2 (2)A(') curve after an avoided crossing with the 3 (2)A(') curve goes down until it meets the X (2)A(') curve. The 2 (2)A(') curve becomes repulsive after the avoided crossing with the X (2)A(') curve. The X (2)A(') curve becomes attractive only after its avoided crossing with the 2 (2)A(') curve. The lowest-lying X (2)A(') potential leads to the HGaSiH(3)X (2)A(') intermediate molecule. This intermediate molecule, diabatically correlated with the Ga((2)S:4s(2)5s(1))+SiH(4) fragments, which lies 1.5 kcal/mol above the ground state reactants leads to the GaH+SiH(3) or H+GaSiH(3) products through the dissociation channels. These products are reached from the HGaSiH(3) intermediate without activation barriers. This work shows that the Ga atom at its first excited state in the presence of silane molecules in gas phase leads to the formation of SiH(3) radicals, H atoms, GaH hydrides, as well as gallium silicide molecules.

The reactions of Cd(1S:5s2,3,1P:5s15p1) and Hg(1S:6s2,3,1P:6s16p1) with SiH4 have been studied through multiconfiguration self-consistent-field (MCSCF) (with relativistic effective core potentials) followed by extensive variational and perturbational second-order multireference Möller–Plesset configuration interaction by perturbation selected by iterative process (CIPSI) calculations using extended Gaussian basis sets. It was found that both metal atoms in their P(ns3np11) state break the Si–H bond of silane spontaneously, leading directly to the MH+SiH3 final products, in agreement with the experimental results of this reaction for Cd. One important qualitative difference between the Cd and Hg(3P) reactions is that for the former an unstable intermediate was found, whereas for the latter no intermediate exists at all. Again, for both atoms, the P(ns1np11) state is also inserted in the Si–H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X1A′ potential surface, adiabatically correlated with the M(1S:ns2)+SiH4 reactants. This interaction leads eventually to the MH+SiH3 products. The structure of these HMSiH3 intermediates, diabatically correlated with the M(1P:ns1np1)+SiH4 reactants, was carefully studied, as well as the dissociation channels leading to the MH+SiH3 and H+MSiH3 products. Accurate energy differences between all these species are also reported. The theoretical results obtained for the mercury reaction are discussed in light of the very recent experimental results of Legay-Sommaire and Legay [J. Phys. Chem. A 102, 8579 (1998)] for the insertion of Hg(3P:4s14p1) in SiH4 over N2 and rare gas matrices. Our results confirm their conclusion that the photochemical insertion of Hg(3P) into the Si–H bond of silane proceeds without any activation barrier.

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.