Structural and dynamical correlations in Ag/sub 2/Se: A molecular dynamics study of superionic and molten phases
We study the structural properties, single-particle dynamics, and the charge transport in superionic and molten Ag/sub 2/Se using the method of molecular dynamics. The calculations are based on a model of interionic potentials in which the ions interact through Coulomb interaction, steric repulsion, and charge--dipole interaction due to the large electronic polarizability of the selenium ions. In the superionic phase the Ag ions diffuse through a stable bcc lattice of Se atoms. Structural and dynamical correlations are studied at five temperatures in the superionic phase and three temperatures in the molten phase. Among the structural correlations the results are presented for partial pair distribution functions, coordination numbers, partial structure factors, bond angle distributions, and the wave vector and temperature dependence of the Bragg intensities. Detailed comparison with the neutron and x-ray single crystal diffraction results are made whenever possible. Diffuse neutron and x-ray scattering is calculated and investigated in detail in the vicinity of q/sub 0/ = (1.6,1,0). It is shown that the anisotropic disks of intensity arise entirely due to the collective motions of silver ions and that these correlations manifest in the q space at a point where the Se--Ag partial structure factor is nearly zero. The calculated temperature dependence of the self-diffusion constant of silver is in good agreement with the tracer diffusion measurements. The spectra of velocity autocorrelation functions and the frequency dependent ionic conductivity are calculated. The Haven's ratio, derived both from the calculated self-diffusion and zero frequency limit of the ionic conductivity, is in good agreement with the experimental results of Okazaki.
- Research Organization:
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439
- OSTI ID:
- 6627101
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 89:12
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MOLTEN SALTS
STRUCTURE FACTORS
SILVER SELENIDES
IONIC CONDUCTIVITY
COMPUTERIZED SIMULATION
DISTRIBUTION FUNCTIONS
NEUTRON DIFFRACTION
SELENIUM IONS
SELF-DIFFUSION
SILVER IONS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
DIFFRACTION
DIFFUSION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FUNCTIONS
IONS
PHYSICAL PROPERTIES
SALTS
SCATTERING
SELENIDES
SELENIUM COMPOUNDS
SILVER COMPOUNDS
SIMULATION
TRANSITION ELEMENT COMPOUNDS
360602* - Other Materials- Structure & Phase Studies
360603 - Materials- Properties