Avoided crossings in metal (M)–gas (X) reactions (M = Hg, and X = SiH4, GeH4)

Novaro, O.; Pacheco-Blas, María del Alba; Pacheco-Sánchez, J. H.

doi:10.1007/s00214-009-0574-4

Cited by 4 publications

(6 citation statements)

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“…We have reported transition probabilities leading toward the product formation of the Au-SiH 4 reactions via an extended version [40][41][42]47,48 of the Landau-Zener 9,10 theory of nonadiabatic transitions at the avoided crossings. Ab initio HF-SCF and MCSCF followed by extensive MR-CI calculations were accomplished to study the Au ͑ 2 S, 2 D, and 2 P͒ ground and excited states plus SiH 4 reactions giving quite good results.…”

Section: Discussionmentioning

confidence: 99%

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

Pacheco-Sánchez

Luna‐García

García-Cruz

et al. 2010

The Journal of Chemical Physics

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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.

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Section: Discussionmentioning

confidence: 99%

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

Pacheco-Sánchez

Luna‐García

García-Cruz

et al. 2010

The Journal of Chemical Physics

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“…The wavy structure showed dislocation near the VGCF-MP interface. MP is believed to bridge the VGCFs by combining the freecarbon atoms in MP with the dangling bonds, which are empty valence orbitals on the surface of immobilized atoms, 18,19) at the VGCF dislocation edges.…”

Section: Resultsmentioning

confidence: 99%

Microstructure Observation of Preform for High Performance VGCF/Aluminum Composites

Lee

Choi

et al. 2014

Mater. Trans.

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Although carbon nanofibers show high thermal conductivities and excellent mechanical properties, their composites do not show superior properties because the short nanofibers are discontinuous. Casting vapor-grown-carbon-fiber-reinforced pure-aluminum-matrix (VGCF/Al) composites requires a continuous VGCF preform carbon lattice and bridging between the VGCFs. We investigated how heating affected mesophase pitch (MP) crystallization and how the VGCFs affected the MP-bridging between the VGCFs used to fabricated VGCF preform. The as-received MP and MP heated at 793 K were prepared, and the crystallinities of the two MPs were compared. The (002)-plane lattice spacing of the MP heated at 793 K was remarkably decreased. The heated-MP showed higher crystallinity than the as-received MP, indicating that the heating affected the crystallinity of the MP. The preform was prepared by heating a 1 : 9 mixture of VGCFs and MP particles at 793 K for 1 h under vacuum below 40 Pa, and the crystallinities were compared with the heated MP. The preform (002) plane showed narrow lattice spacing comparable to that of heated MP, the preform showed higher crystallinity than the heated MP, indicating that the VGCFs affected the crystallinity of the MP. The MP enclosed rather than bridged the VGCFs. Moreover, the VGCFs were randomly oriented throughout the MP. The microstructures of the VGCF consisted of linear and wavy carbon structures. The fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) analyses indicated that the wavy structure showed dislocation.

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“…The formation of the HHgSiH 3 intermediate arising at the minimum (106 kcal mol −1 , 70 • ) comes with 6p 1 character and passes through an avoided crossing between trajectories 2 1 A and X 1 A of the energy surfaces maintaining 6p 1 character. The transition probability [84] at the avoided crossing among the latter states is obtained when mercury is photoexcited to the Hg 1 P: 5d 10 6s 1 6p 1 excited state, allowing it to be inserted in silane (SiH 4 ) molecule. When the reaction pathway passes the crossing point and continues its way has a probability P = 0.79 of crossing toward curve X 1 A with 6p 1 character and a probability of P = 0.21 of continuing in the same curve 2 1 A (see Figure 10) with 6s 2 character.…”

Section: Amentioning

confidence: 99%

“…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)). The transition probability [84] between the PES is obtained for the reaction Hg 1 P(5d 10 6s 1 6p 1 ) + GeH 4 → Hg 1 S(5d 10 6s 2 ) + GeH 4 . When mercury is photoexcited to the Hg ( 1 P:5d 10 6s 1 6p 1 ) second excited state, the mercury atom is inserted in germane (GeH 4 ) molecule.…”

Section: Amentioning

confidence: 99%

“…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. Transition probability theory is described here when the reaction parameter is distance or angle.…”

Section: Introductionmentioning

confidence: 99%

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