Collective excitations and viscosity in liquid Bi

Abstract

Liquid structure and temperature invariance of sound velocity in supercooled Bi melt J. Chem. Phys. 140, 094502 (2014) The analysis of extensive density functional/molecular dynamics simulations (over 500 atoms, up to 100 ps) of liquid bismuth at four temperatures between 573 K and 1023 K has provided details of the dynamical structure factors, the dispersion of longitudinal and transverse collective modes, and related properties (power spectrum, viscosity, and sound velocity). Agreement with available inelastic x-ray and neutron scattering data and with previous simulations is generally very good. The results show that density functional/molecular dynamics simulations can give dynamical information of good quality without the use of fitting functions, even at long wavelengths. Published by AIP Publishing.[http://dx

Density functional study of structure and dynamics in liquid antimony and Sbn clusters

“…The dynamical structure factor S(q, ω) is determined from the current autocorrelation functions as described in detail in Ref. 68. The shear viscosity η couples to the transverse momentum and can be calculated from the transverse current autocorrelation function and its Laplace transform.…”

“…Full details are provided in Ref. 68. A simple connection between viscosity η and diffusion constant or diffusivity D is the Stokes-Einstein relationship (SER) 82,83 derived for the diffusion of uncorrelated macroscopic spheres in a liquid,…”

“…The hexagonal symmetry is compatible with that of bulk Sb, as the results formed a part of a continuing study of crystallization of liquid Sb. 69 The densities at the melting point and above were taken from Ref. 78, and those of supercooled samples were assumed to be the same as at 900 K. The time step was 3.025 fs.…”

“…Ballone and Jones 66 studied the liquid-liquid phase transition in a 4000-atom sample of P using a classical force field with parameters fit to an extensive set of DF calculations on phosphorus clusters. Most recently, we performed DF/MD simulations on liquid Bi at four temperatures between 573 K and 1023 K. 67,68 These simulations provided much information on the structure and dynamics of liquid Bi, including collective excitations, and also of Bi n clusters with n ≤ 14. 67 We present here the results of DF calculations of the structures and energies of Sb n clusters up to n = 14 and compare where possible with other calculations (DF and correlated wave functions) and with the experiment.…”

“…We also describe extensive DF/MD simulations of liquid Sb (melting point 903.8 K) at six temperatures between 600 K and 1300 K. The latter forms a part of a continuing study of the rapid crystallization of liquid Sb. 69 We study structural patterns (coordination numbers, bond angles, and ring statistics), structure factors, pair distribution functions, and dynamical properties (vibration frequencies, diffusion constants, power spectra, dynamical structure factors, viscosity) and compare with available experimental results and the results of our Bi simulations. We comment on the evidence for Peierls distortions at different temperatures and the limitations of the approximate exchange-correlation energy functionals used in our calculations.…”