Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study of the structure of silver clusters (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2165-2177 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutral silver cluster isomers Agn (n=2 to 12) were studied by Kohn–Sham density functional theory. There is a strong even-odd oscillation in cluster stability due to spin subshell closing. Nearest-neighbor interatomic distances do not evolve continuously from the diatomic (2.53 Å) to the bulk (2.89 Å). After adding an empirical correction to the calculated values, we estimate that they are always near 2.68 Å for 3≤n≤6, and near 2.74 Å for 7≤n≤12. We find several low-energy isomers at all cluster sizes larger than seven atoms with one exception: Ag10 has a D2d twinned pentagonal bipyramid isomer predicted to be 0.20 eV more stable than any other isomer. The ellipsoidal jellium model predicts rather well the shapes of stable silver clusters. Other models (extended Hückel, empirical potential) fail to reproduce the energy ordering of cluster isomers. The structural attributes of low-energy silver cluster isomers Agn (n≥7) are, in decreasing order of importance: a high mean coordination; a shape that conforms to the ellipsoidal jellium model; and uniformity in atomic coordinations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383288
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A density functional study of FeCO, FeCO−, and FeCO+ (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8233-8239 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The binding energies, structural parameters, and vibrational frequencies of FeCO, FeCO−, and FeCO+ were studied with a linear combination of Gaussian-type orbitals-density functional (LCGTO-DF) method. The ground state of FeCO is found to be 3Σ− and the calculated dissociation energy, with respect to ground state Fe(5D,3d64s2) and CO (1Σ+), is 30 kcal/mol; after correcting for the atomic states separation of the iron atom this value becomes 17 kcal/mol, which is relatively close to the most recent experimental values 8.1±3.5–10.5±3.7 kcal/mol. Quartet ground states were found for both FeCO+ and FeCO− and the calculated dissociation energies (with respect to ground state Fe+, Fe−, and CO) are 50 and 31 kcal/mol, respectively. There is agreement between theory and experiment in that D(FeCO+)(approximately-greater-than)D(FeCO−)(approximately-greater-than)D(FeCO). The ωe's we calculate for FeCO are, in cm−1, 658 (Fe–C stretch), 1982 (C–O stretch), and 368 (bend). These values are reasonably close to their experimental counterparts, 530±10, 1950±10, and 330±50. For FeCO− we have found 566 and 272 cm−1 for the Fe–C stretch and bend modes while the experimental values are 465±10 and 230±40 cm−1. A frequency of 1831 cm−1 is predicted for the C–O stretch of FeCO−. The σ-donation (CO→Fe) and π-back-donation (Fe→CO) charge transfer mechanism is operative in these species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466766
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Theoretical study of the bonding of ammonia, carbon monoxide, and ethylene, to copper atom, dimer, and trimer (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5396-5407 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Kohn–Sham density functional theory (KS-DFT) calculations were performed for the association complexes Cun–L, with n=1, 2, 3 and L=NH3, CO, and C2H4. Two geometries for Cu2–L are considered; with the ligand bonded to a single copper atom ("atop,'' or A), and with the ligand bonded to both atoms ("bridge,'' or B). In addition to A and B, a third geometry was considered for Cu3–L, with the ligand bonded to all three copper atoms; in each case, no minimum was found for that third geometry. I report fully optimized equilibrium geometries and harmonic frequencies calculated within the local spin density (LSD) approximation for all the bound complexes and estimates of their binding energies obtained with a gradient-corrected exchange-correlation functional. Structure A is the most stable in all cases but, for Cu3CO and Cu3C2H4, structure B is only a few kcal/mol higher in energy. The energetic contribution from the geometrical relaxation of Cu3 ranges from essentially zero (Cu3NH3 B) to 3.4 kcal/mol (Cu3CO B). In agreement with previous calculations on Cun–C2H2 and with experiments, the calculated Cun–L binding energy is found to increase with n for all ligands. Although the bonding mechanism differs among the three ligands, repulsion of a filled ligand orbital with the half-filled 4s orbital of copper (or 4s-derived molecular orbitals of Cu2 and Cu3) always plays an important role and is responsible for the smaller binding energies in the CuL complexes. This repulsion decreases from Cu to Cu2 because of charge accumulation in Cu–Cu midbond region and of the greater polarizability of Cu2. The Cu3L binding energies are larger than those of Cu2L mostly because of the greater involvement of copper 4p orbitals in bonding to the ligand. The ligand vibrational frequency shifts relative to the free molecules are compared to experiment and discussed in relation to the nature of the metal–ligand interaction. In particular, an interesting correlation, between the frequency of the NH3 umbrella mode and the metal–NH3 binding energy, is likely due to the electrostatic nature of the bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469267
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Vibrational and geometric structures of Nb3C2 and Nb3C+2 from pulsed field ionization-zero electron kinetic energy photoelectron spectra and density functional calculations (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10663-10671 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational frequencies of three niobium normal modes of triniobium dicarbide neutral and cation have been determined from pulsed field ionization-zero electron kinetic energy photoelectron spectra. The niobium stretching mode has a frequency of 326 cm−1 in the neutral and 339 cm−1 in the ion. The two deformation modes have frequencies of 238 and 82 cm−1 in the neutral and a degenerate frequency of 258 cm−1 in the ion. The geometry of the triniobium dicarbide has been established by comparing the experimental spectra with theoretical calculations. The cluster has a trigonal bipyramid geometry with carbon atoms capping on each face of the metal frame. The cation cluster has D3h symmetry whereas the neutral cluster has lower symmetry resulting from a Jahn–Teller distortion. A second low-lying structure with doubly bridging carbon atoms has been identified by the calculations but has not yet been observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472873
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Singlet- and triplet-state (ethene)nickel: a density functional study (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 9986-9991 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100141a016
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Dissociation dynamics of D2 on rigid and nonrigid Ni clusters (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 1530-1539 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present results of a theoretical study of the dissociation dynamics of D2 on NiN clusters with N=3–13. First, the semiempirical density functional based molecular dynamics/Monte Carlo corrected effective medium method was used to predict the interaction energies of various Ni clusters in this size range. We identified the most stable clusters and found that only N=9 possesses two nearly equally stable isomers with an energy difference of only 0.03 eV. Second, we performed classical trajectory simulations of the reactions in which the Ni atoms were allowed to move. The dissociation cross sections from calculations on the nonrigid clusters were nearly equal to those obtained with the rigid Ni cluster. A particularly intriguing result was that the dissociation cross sections calculated for the two isomers of Ni9 differed significantly, especially at low collision energy. Third, we showed that the dissociation probabilities as functions of the impact parameter and relative translational energy were fit with good accuracy as a simple function of a single variable E⊥, the component of translational energy perpendicular to the surface of the cluster. This indicated that the normal energy scaling of the dissociative sticking probability observed in some gas/surface systems may have an equivalent behavior in gas/cluster systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462137
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Theoretical study of the monocarbonyls of first-row transition metal atoms (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 1801-1815 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The results of density functional calculations on the most stable high-spin and low-spin states of MCO are given, where M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. The ground states are found to be high spin for M=Sc, Ti, V, Cr, and Cu (2S+1=4, 5, 6, 7, and 2, respectively) and low spin for M=Mn, Fe, Co, and Ni (2S+1=4, 3, 2, and 1, respectively). From Sc to Cu, the M–CO binding energies with respect to ground state products are estimated to be 9, 16, 26, 13, −14, 14, 30, 54, and 19 kcal/mol. Where comparison with experiment is possible, the estimates are apparently too large by about 6 kcal/mol (FeCO), 13 kcal/mol (NiCO), and 12 kcal/mol (CuCO). The high-spin state MCO complexes with metal to the right of vanadium in the Periodic Table all have bent equilibrium geometries; all others are found to be linear. The calculated CO harmonic stretch frequencies generally overestimate the observed values, but follow a similar trend. The CO bond lengths, CO stretch frequencies, and metal–CO bond strengths all correlate well with the extent of π back donation. However, these correlations hold only within either the group of all high-spin states, or the group of all low-spin states. Thus, there are no simple trends in the calculated properties of ground state MCO complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465297
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Electronic spectroscopy of the niobium dimer molecule: Experimental and theoretical results (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8504-8518 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved electronic spectra of the niobium dimer molecule are reported for the first time. The molecules were produced by laser vaporization of a niobium target rod and cooled in a helium supersonic expansion. The molecular beam containing niobium dimer molecules was interrogated in the range 400–900 nm using a pulsed dye laser to excite fluorescence. Numerous Ω=0←Ω=0 and Ω=1←Ω=1 vibronic transitions were discovered in the region 630–720 nm and investigated at 200 MHz resolution using the cw output of a single mode ring dye laser. The principal features were classified into five Ω=0←Ω=0 systems originating from a common lower state of 0+g symmetry, and three Ω=1←Ω=1 systems originating from a common lower state of 1g symmetry. The two lower states were assigned as the Ω=0 and Ω=1 spin–orbit components of the X 3Σ−g ground state, which is derived from the electron configuration 1π4u1σ2g2σ2g1δ2g. The two spin–orbit components are split by several hundred cm−1 due to a strong, second-order isoconfigurational spin–orbit interaction with the low-lying 1Σ+g state. Evidence for significant 4d orbital participation in the Nb2 bond is furnished by the short bondlength [re=2.077 81(18) A(ring)] and large vibrational frequency [ωe=424.8917(12) cm−1] determined for the X 3Σ−g(0+g) state (2σ error bounds). The electronic structure of niobium dimer was investigated using density functional theory. For the electronic ground state, the predicted spectroscopic properties were in good agreement with experiment. Calculations on excited states reveal congested manifolds of triplet and singlet electronic states in the range 0–3 eV, reflecting the multitude of possible electronic promotions among the 4d- and 5s-based molecular orbitals. The difficulties of correlating the experimentally observed electronic transitions with specific valence electronic promotions are addressed. Comparisons are drawn between Nb2 and the isoelectronic molecule V2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465627
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Theoretical study of linear and bent CrCO, NiCO, and CuCO (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 8041-8050 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: I performed density functional calculations on the electronic ground state of the monocarbonyls of chromium, nickel, and copper. CrCO and CuCO have bent equilibrium geometries with angles equal to 139.9° and 143.9° respectively, while NiCO is linear. The linear structures of CrCO and CuCO are less stable by 3 kcal/mol and are not minima, but have two imaginary frequencies. An analysis of the bonding suggests that the bent structures of CrCO and CuCO are more stable because the repulsion between the 5σ orbital of CO (essentially a lone pair on the carbon atom) and the half-filled orbital on the metal is smaller in that geometry. The calculated Ni–CO bond energy 53 kcal/mol is 13 kcal/mol larger than the most recent experimental determination [L. S. Sunderlin et al., J. Am. Chem. Soc. 114, 2788 (1992)]. The calculated bond energies of CrCO and CuCO are 14 and 20 kcal/mol, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464559
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Erratum: Density functional study of the bonding in small silicon clusters [J. Chem. Phys. 97, 4149 (1992)] (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 9222-9222 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465119
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...