<i>Ab initio</i>calculation of melting and thermodynamic properties of crystal and liquid aluminum

Straub, Galen K.; Aidun, John B.; Wills, J. M.; Sanchez-Castro, Carlos; Wallace, Duane C.

doi:10.1103/physrevb.50.5055

Cited by 45 publications

(20 citation statements)

References 36 publications

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“…Since we will be testing the EOS by comparison with Hugoniot data, we will always be in the high-T region (except for one brief low-T excursion; see below), so we use Eq. (6) for F To determine these functions, we began by consulting the results of density functional theory (DFT) calculations carried out in the local density ap-proximation by Straub et al [7]. They worked with fcc and bcc Al at atomic volumes from 37 a 3 0 to 160 a 3 0 , where a 0 is the Bohr radius, corresponding to densities from 8.17 g/cm 3 to 1.89 g/cm 3 (the density of Al at 293 K and 1 bar is 2.700 g/cm 3 ).…”

Section: Constructing the Eosmentioning

confidence: 99%

“…The pseudopotential was then used to calculate phonon frequencies throughout the Brillouin zone, allowing the determination of Θ Table 1 and Figure 1. (The full set of results was not reported in [7].) To check these results, Straub et al compared experimental phonon moments for Al at T = 80 K and P = 1 bar based on Born-von Karmen fits to neutron scattering data [9] with their predictions interpolated to the appropriate atomic volume of 110.7 a 3 0 .…”

Section: Constructing the Eosmentioning

confidence: 99%

“…332-334 of [10] and their values for various n are tabulated in [11,12]. [7]. The free electron n s (ǫ) at this volume and Z = 3 from Eq.…”

Section: Constructing the Eosmentioning

confidence: 99%

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Test of a theoretical equation of state for elemental solids and liquids

2003

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We propose a means for constructing highly accurate equations of state (EOS) for elemental solids and liquids essentially from first principles, based upon a particular decomposition of the underlying condensed matter Hamiltonian for the nuclei and electrons. We also point out that at low pressures the neglect of anharmonic and electronphonon terms, both contained in this formalism, results in errors of less than 5% in the thermal parts of the thermodynamic functions. Then we explicitly display the forms of the remaining terms in the EOS, commenting on the use of experiment and electronic structure theory to evaluate them. We also construct an EOS for Aluminum and compare the resulting Hugoniot with data up to 5 Mbar, both to illustrate our method and to see whether the approximation of neglecting anharmonicity et al. remains viable to such high pressures. We find a level of agreement with experiment that is consistent with the low-pressure results.

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Section: Constructing the Eosmentioning

confidence: 99%

Section: Constructing the Eosmentioning

confidence: 99%

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Test of a theoretical equation of state for elemental solids and liquids

2003

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“…Because of its simple electronic structure, aluminum metal is frequently used as a test case for theoretical models of crystals and their thermodynamics. [1][2][3][4][5][6][7][8][9][10] Aluminum is nonmagnetic, so the majority of its entropy comes from phonons. In turn, the majority of its phonon entropy S ph can be attributed to harmonic oscillations of the nuclei about their equilibrium positions.…”

Section: Introductionmentioning

confidence: 99%

Phonons in aluminum at high temperatures studied by inelastic neutron scattering

et al. 2008

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Inelastic neutron scattering measurements on aluminum metal were performed at temperatures of 10, 150, 300, 525, and 775 K using direct-geometry Fermi chopper spectrometers. The temperature dependent phonon density of states ͑DOS͒ was determined from the scattering, and was used to fit Born-von Kármán models of lattice dynamics. The shifts in the phonon frequencies with increasing temperature were largely explained by the softening of the longitudinal force constants out to third nearest neighbors. A significant broadening of the phonon spectra at high temperatures was also measured. The phonon DOS was used to determine the vibrational contributions to the entropy of aluminum as a function of temperature. All other contributions to the entropy of aluminum were calculated or assessed, and the total entropy was in excellent agreement with the NIST-JANAF compilation ͓M. W. Chase, J. Phys. Chem. Ref. Data Monogr. 9, 59 ͑1998͔͒. Anharmonic effects were attributed to phonon-phonon interactions. The quasiharmonic approximation was generally successful, but its weaknesses are discussed.

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“…Zone boundary phonons were calculated for TiAl and NiAl as a function of volume. These are being used, together with calculated elastic constants, to fit interatomic potentials to be used in the calculation of the EOS of these materials (Straub, 1994). Calculations of vacancy structures and formation energies in the Laves phase intermetallic NbCr(2) were performed using 24-atom supercells.…”

Section: Scientific Approach and Accomplishmentsmentioning

confidence: 99%