Validation of a glue-model approach in a tight-binding hard-sphere model for hot fluid metals

E. Chacón, M. Reinaldo-Falagán, P. Tarazona, E. Velasco, and J. P. Hernandez

Phys. Rev. B 71, 024204 – Published 21 January 2005

Abstract

We have calculated thermodynamic, structural, and electronic properties of a model fluid of monovalent atoms which interact via hard-sphere repulsions and an attraction arising from the delocalization free energy of the valence electrons. These properties result from self-consistent Monte Carlo simulations of equilibrium ionic structures based, at each step in which an ion is to be moved, on the exact electronic free energies corresponding to the ionic configurations. The electronic energy is derived from a tight-binding model with electronic hopping which decays exponentially with distance. The liquid-vapor coexistence curve and both ionic and electronic structures are obtained. By direct comparisons, the present results confirm previous ones which were obtained basing the simulations on a glue-model description of ion energies. The importance of this confirmation is the validation of the glue-model approach, one of the few computational simplifications possible for realistic metallic fluids.

Received 23 April 2004

DOI:https://doi.org/10.1103/PhysRevB.71.024204

Authors & Affiliations

E. Chacón¹, M. Reinaldo-Falagán², P. Tarazona², E. Velasco², and J. P. Hernandez³

¹Instituto de Ciencia de Materiales de Madrid, CSIC, E-28049 Madrid, Spain
²Física Teórica de la Materia Condensada (C-V) Universidad Autónoma de Madrid, E-28049 Madrid, Spain
³Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599-3255, USA

Electrical conductivity of a tight-binding hard-sphere model for hot fluid metals

P. Tarazona, E. Chacón, J. A. Vergés, M. Reinaldo-Falagán, E. Velasco, and J. P. Hernandez

Phys. Rev. B 71, 024203 (2005)

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 71, Iss. 2 — 1 January 2005

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Liquid-vapor phase coexistence results. At low temperature the coexistence is solid vapor. The open circles (and dotted line connecting them) are the previously published results using the glue model with a MC NVT-slab simulation technique and $N = 1500$ . The square symbols represent the present results based on the exact energy evaluations with $r_{cut} = 3.1 d_{HS}$ : the open squares (and dashed line connecting them) result from the NPT simulations with $P = 0$ and $N = 256$ , and the filled squares from Gibbs-ensemble simulations $(N = 350)$ . The filled triangles represent Gibbs-ensemble simulation results $(N = 350)$ using the exact energies but now without truncating the electronic hopping.Reuse & Permissions
Figure 2
Phase coexistence from NPT $P = 0$ $(N = 256)$ and Gibbs-ensemble $(N = 350)$ simulations compared to each other and to previous work (results also shown). Open circles (and dashed line connecting them) are the previously published results using NVT-slab simulations $(N = 1500)$ . Semifilled circle (at the lowest temperature) NPT $P = 0$ , $N = 256$ simulation. Filled circles are results from the Gibbs-ensemble $(N = 350)$ simulations. All the above results are based on the same glue-model energies. The filled squares (as in Fig. 1) are results from the Gibbs-ensemble simulations based on the exact energies but without truncating electronic hopping.Reuse & Permissions
Figure 3
Radial distribution functions $g (r)$ obtained from MC-NVT simulations, for a low density expanded liquid ( $T * = 0.15$ and $ρ * = 0.344$ ). We compare the $g (r)$ arising from using exact energies with $N = 256$ (solid line), that arising from using the glue-model energies with $N = 500$ (dashed line), and the one obtained using the HS correlations only (dotted line).Reuse & Permissions
Figure 4
Radial distribution functions $g (r)$ obtained from MC-NVT simulations at a high density vapor, near the transition region from metallic to nonmetallic behavior ( $T * = 0.1575$ and $ρ * = 0.03$ ). Lines as in Fig. 3.Reuse & Permissions
Figure 5
Calculated static structure factors, for three points on the glue-derived liquid-vapor coexistence curve. The full lines are results from our MC-NVT simulations ( $N = 256$ particles) determined by the exact energies; the dashed lines from our MC-NVT simulations ( $N = 500$ particles) using the glue-model energies; the dotted lines are calculated assuming only HS correlations among the ions. The vertical thin line indicates the position of maxima of $S (k)$ at high density, as a reference to its position for the lower densities shown. The three densities ( $T *$ values are noted in text) correspond to (a) $ρ * = 0.344$ (a low density expanded liquid), (b) $ρ * = 0.175$ (a density very close to our estimate for the critical point), and (c) $ρ * = 0.03$ (a vapor, in the transition region from metallic to nonmetallic behavior, see Refs. 1, 6).Reuse & Permissions
Figure 6
Electronic density of states per ion $Γ (E)$ as function of $E ∕ t_{o}$ for the same three sets of conditions as in Fig. 5. The full lines give the results obtained using ionic configurations from our MC-NVT simulations ( $N = 256$ particles) based on the exact energies; the dashed lines from our MC-NVT simulations ( $N = 500$ particles) using the glue-model energies; the dotted lines are calculated assuming only HS correlations among the ions.Reuse & Permissions

Physical Review B

covering condensed matter and materials physics