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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1449-1458 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The unstable structural responses of a model intermetallic lattice to hydrostatic and uniaxial loadings have been determined by elastic stability analysis and molecular-dynamics simulations. Two crystalline phases of Ni3Al, the naturally occurring L12 and a hypothetical D022, are analyzed to correlate the effects of structural symmetry with stress-induced lattice deformations. Under isotropic expansion, the former fcc lattice develops extensive cavitation and amorphization at critical isotropic tensile loading, whereas the latter, a tetragonal lattice, shows cleavage behavior. These qualitative differences do not appear in the elastic stability analysis. Both phases show similar responses to uniaxial tension. In all cases critical strains for lattice instability predicted on the basis of elastic stiffness coefficients are found to be in good agreement with direct simulations. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2719-2725 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Brittle fracture of β-SiC (polytype 3C) under hydrostatic tension has been modeled by molecular dynamics simulation using an interatomic potential function that treats the solid as fully covalent. The critical stress at which the lattice becomes structurally unstable is shown to agree quantitatively with that predicted by stability analysis based on elastic stiffness coefficients. The instability mode is the spinodal (vanishing of bulk modulus), and decohesion occurs as spontaneous nucleation of cracking on {111} shuffle planes. Atomic relaxation on the newly generated cracked surfaces appears to take place immediately following crack opening.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 96-106 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermodynamic properties of silicon (diamond cubic phase) are calculated using an empirical many-body potential developed by Tersoff [Phys. Rev. Lett. 56, 632 (1986)] based on the concept of bond order. It is shown that this model gives predictions in good agreement with experiment for those properties governed by energetics (free energy, entropy, and heat capacity). The thermal expansion coefficient is less well described, which is traced to the fact that the model potential, in its present version, is overly stiff and therefore unable to account properly for the volume dependence of the transverse acoustic modes. Furthermore, sensitivity of the potential to whether each atom remains bonded to only four neighbors indicates that the short-range nature of the potential may necessitate model improvement before it is suitable for studies of thermomechanical properties at elevated temperatures or large deformations. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3216-3221 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulation of isobaric heating of an H2O lattice with diamond cubic structure reveals a distinct two-step sequence of hydrogen-bond breaking in a temperature range clearly below the melting point. Partial breakage, signaled by an abrupt increase in local atomic coordination and the coupling of intermolecular torsions with intramolecular angle bending, first occurs and leaves the lattice in a fragmented but still ordered state. This is then followed by full breakage at a temperature about 20–30 K higher, bringing the lattice to an orientationally disordered state characterized by a vibrational spectrum similar to that of water.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4009-4014 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A structural transition bcc→hcp induced by uniaxial tensile stress is observed by molecular dynamics simulation using an interatomic potential function for α-iron derived by the embedded atom method. The transformation is reversible with hysteresis. The deformation mechanism for the forward transition is found to be different from that for the backward transition. The critical stress required for the transition decreases with increasing temperature, as is expected.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5688-5690 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The distribution of local stress in an atomic system can be calculated from its mechanical definition. While this leads, for a homogeneous system, to an expression equivalent to that derived from the virial theorem (thermodynamic definition), when local inhomogeneities are present the equivalence can be demonstrated only in the sense of a volume average which effectively eliminates the inhomogeneities. Atomistic simulation results are presented to show that for a relaxed crystal with a planar free surface, the normal stress on each atomic plane parallel to the surface, when calculated according to the mechanical definition, vanishes uniformly as expected, whereas if the virial expression were applied the resulting stress distribution shows unphysical oscillations in the surface region.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2088-2096 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Guided by a recent molecular dynamics simulation study of mode I crack-tip environment in α-Fe using an embedded atom method potential, an activation analysis of the nucleation of a half-square dislocation loop from the tip of a tensile crack has been carried out based on the Rice and Thomson approach [Philos. Mag. 29, 78 (1974)]. The effects of elastic softening due to stress and temperature as well as the nonlinear stress distribution around the crack are introduced by incorporating the simulation results self-consistently into the analysis, reducing the previously overestimated activation barrier by a factor of over 15.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4078-4089 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulations of liquid (305 K) and solid (10 K) benzene have been carried out to investigate the vibrational properties of benzene in the condensed phase. The benzene molecule is modeled as a fully flexible system of 12 atoms with intramolecular interactions based on ab initio harmonic potentials and intermolecular interactions given by semiempirical atom–atom potentials. Vibrational frequencies are analyzed in terms of the frequency spectrum of the velocity autocorrelation function and the results are found to correlate well with optical absorption and scattering data. Single particle density fluctuations are calculated over a range of wave numbers and results are obtained that can be directly compared to the intensity distributions of inelastically scattered thermal neutrons. The different comparisons indicate that the existing potential energy function provides an essentially quantitative description of molecular vibrations of benzene.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1726-1732 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dielectric properties of liquid water are studied using an empirical potential model treating the monomers as flexible molecules with short-range interactions between oxygens and Coulomb interactions between charges situated on the individual atoms. Satisfactory results for the static dielectric constants at 259, 300, and 350 K are obtained from long simulation runs; these constitute a significant improvement over recent calculations using other potential models. Time correlation functions of dipole moment and single molecule orientation are evaluated. In the supercooled state an enhanced slowing down in the temporal decay of polarization fluctuations occurs, a behavior essentially absent in the single molecule reorientations. Good agreement is found in the self-diffusion coefficient over the entire temperature range.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 4056-4064 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A study is made of the feasibility of predicting the dynamical properties of liquid and solid hydrocarbons by means of molecular dynamics simulations using an empirical force field CFF developed for an entire family of alkanes. Results for mean square displacements and velocity autocorrelation functions are presented for liquid n-butane (C4H10). Vibrational frequencies are examined through a generalized density of states and compared with optical data. The van Hove correlation function for the protons is calculated and the result leads to a semiquantitative prediction of the energy distribution of neutron inelastic scattering. A certain deficiency of the force field is indicated by the present results.
    Type of Medium: Electronic Resource
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