ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    Multiple-band theory of dynamics for interacting adsorbates coupled to phonons. II. Single adsorbate dynamics (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 6975-6990 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of an adsorbate described by a two-band generalization of the small-polaron model [J. Chem. Phys. 95, 8599 (1991)] are investigated. Lattice induced mixing of the bands can result in the adsorbates becoming self-trapped at one end of an adsorption site or the other. Tunneling between adjacent sites can either preserve or change the end of the site in which the adsorbate resides. The associated rates have very different temperature and mass dependences, and contribute to the overall diffusion in very different ways. The observed equilibrium and transport properties of the H/W(110) system can be consistently explained within our model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463213
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Multiple-band theory of dynamics for interacting adsorbates coupled to phonons. I. Variationally optimized Hamiltonian (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 8599-8615 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A two-band generalization of the Hubbard model is developed in order to examine the different roles of adsorbate interactions with one another and with phonons. Variationally optimized unitary transformations of the Hamiltonian are performed in order to obtain dressed tunneling amplitudes. These display strong dimensional dependence and demonstrate fundamental differences between the effects of coupling of adsorbate density and of adsorbate vibrational excitation to the lattice modes. The occurrence of on-site asymmetric self-trapping induced by even weak coupling of interband excitations to the lattice is demonstrated, and the effect of this on the thermally averaged, intersite tunneling is investigated. Implications for surface transport and for surface reconstructions of hydrogen/metal systems are made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461239
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A mean-field theory of grain boundary segregation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4427-4438 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper presents a mean-field solution for a one-dimensional spin Hamiltonian in the presence of spatially varying interactions and external field. In a binary alloy, such inhomogeneous interactions appear in the presence of a grain boundary. We derive the model and place it in the context of previous theories. We show how our theory is a natural extension of traditional segregation isotherm models, with the advantages that much finer detail can be observed and that no assumption is required about the grain boundary binding energy. Solving the model requires finding the global minimum of a function of several hundred variables and yields detailed concentration profiles in the presence of spatially inhomogeneous and long-range interactions. We apply the theory to the system of copper with bismuth impurities and observe on an atomic scale how the extent of segregation varies with temperature. The results predict that with lower temperature the impurity concentration in a given layer increases, the segregant peak broadens, and ordering can occur within the boundary. The results also indicate that the presence of segregation at the grain boundary can serve as a nucleus for order–disorder phase transitions in the bulk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461766
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Monte Carlo studies of grain boundary segregation and ordering (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3674-3687 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper describes a systematic microscopic study of solute segregation and ordering at a grain boundary. We develop for this inhomogeneous system several Monte Carlo techniques and apply these to analyze the distribution of substitutional impurities near a symmetric coincident-site-lattice tilt boundary. The calculations demonstrate the importance of ensemble and boundary condition for a Monte Carlo simulation, especially one with an inhomogeneous lattice and with ordering, as opposed to segregating, bulk interactions. The resulting concentration profiles exhibit segregation to the boundary at high temperatures and bulk ordering at low temperature. Based on our results, we propose a mechanism for a solid–solid interfacial ordering phase transition previously suggested by experiment. We also compare these simulations to our earlier one-dimensional mean-field work and find that the three-dimensional simulations confirm the essential mean-field predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462950
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Many-particle quantum dynamics: An exact algorithm for correlated motion on lattices (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5318-5333 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The time dependent many-body dynamics of strongly interacting particles on a two-dimensional lattice are studied with the recently developed checkerboard propagator. Application is made to the two-dimensional infinite U Hubbard model at high concentrations, for both fermion and boson systems. The concentration, initial state, and boundary condition dependence of vacancy correlation functions are analyzed, and related to the local densities of states. Quasidissipative behavior of the correlation functions is seen beyond a short initial time scale during which single-particlelike motion is seen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462717
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Quantum relaxation in high density fermion and boson tunneling dynamics: Implications for low temperature anomalous surface diffusion (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1417-1420 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum relaxation behavior for many-particle tunneling systems of interacting identical particles is studied for both fermions and bosons within the infinite U Hubbard model, using a numerically exact checkerboard time propagation. Dependence of relaxation times upon vacancy concentration is obtained, and conclusions for nuclear statistical effects in hydrogen surface diffusion presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461123
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Electronic structure of semiconductor nanoclusters: A time dependent theoretical approach (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 3707-3715 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a time dependent theoretical approach to calculating the electronic properties of semiconductor nanoclusters. The technique can be applied to ground and excited electronic states without using the effective mass approximation or perturbative expansions. The effects of surface properties on the electronic structure can be calculated at an atomic level. We illustrate the method with calculations of ground state densities of states for CdS and CdSe crystallites between 19 and 33 A(ring) in diameter. The size-dependence of the bandwidths and band gap is studied, and the influence of surface states and surface polarity is discussed. The calculated shift in the valence band edge with cluster size is compared with experimental results from valence-band photoemission. Good agreement is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466146
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Rotational excitations of quantum liquid clusters: He7 and (H2)7 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8816-8829 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have studied the quantum clusters, He7 and (H2)7, in their ground (L=0) and rotationally excited states (L=2–8 for He and L=2–12 for H2) by variational Monte Carlo, and selectively by diffusion Monte Carlo. The optimized trial wave functions are eigenfunctions of L2, and, as such, are orthogonal and yield upper bounds to the energy of each state. We report energies and structural results, including density profiles and moments-of-inertia distributions. Overall, the He7 cluster is more delocalized than the (H2)7 cluster, but the computed structures show that both He7 and (H2)7 are highly nonclassical and nonrigid, evolving from spherical to toroidal structures as the angular momentum increases. We find that by L=2 for He7 and by L=6 for (H2)7, the clusters become metastable with respect to dissociation, as determined by comparison of excited-state energies of the N=7 clusters with the ground-state energies for N=6. The root-mean-square bond length fluctuations indicate that both N=7 clusters are liquidlike in the L=0 ground state, according to the Lindemann criterion. These fluctuations increase with L, implying a further decrease in rigidity for the rotationally excited states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465550
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Theoretical analysis of the geometries of the luminescent regions in porous silicon (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1125-1127 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The luminescence energies of a variety of crystalline silicon nanostructures are calculated using a time-dependent tight-binding technique. The calculated energies are compared with measured values for porous silicon samples to determine the geometries of the regions in which electron-hole recombination occurs. We observe a correlation between luminescence wavelength and nanostructure which is consistent with the porosity changes during the etching process. We conclude that porous silicon samples which emit visible light are composed of small crystallites, and that the active regions in longer wavelength emitters are wirelike structures. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114982
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Path integral Monte Carlo study of SF6-doped helium clusters (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 2341-2348 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The path-integral Monte Carlo technique is applied to study the SF6He39 cluster at low temperatures. The method employs as input only pair potentials, the number of atoms, and the temperature, and is thus independent of the trial function bias which can affect calculation of structural quantities in variational and diffusion Monte Carlo. We thereby obtain an unambiguous answer to the question of the location of SF6 in small clusters (39 He atoms), as well as the temperature dependence of the cluster structure. The cluster is found to undergo a gradual transition to a superfluid between 0.625 K and 1.25 K, and to evaporate significantly at temperatures above 2 K. We also calculate spectral shifts for the ν3 vibrational mode of SF6, using the instantaneous dipole-induced dipole mechanism. The results are compared with infra-red absorption measurements and with the previous ground-state quantum Monte Carlo calculations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470929
    Location Call Number Expected 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...