Cell-cluster and self-consistent calculations for a model sodium chloride crystal

Cowley, E. R.; Gross, Jeferson; Gong, Zhaoxin; Horton, G. K.

doi:10.1103/physrevb.42.3135

Cited by 24 publications

(18 citation statements)

References 13 publications

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“…Additionally, it usually requires use of the quasi-harmonic approximation, and anharmonic effects are usually neglected. The PIC model is a mean field approximation to the thermal contribution 20,21 . It includes on-site anharmonicity and requires less computer power when combined with first-principles totalenergy calculations.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Lattice dynamics and thermodynamics of bcc iron under pressure: First-principles linear response study

Sha

Cohen

2006

Phys. Rev. B

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We compute the lattice-dynamical and thermal equation of state properties of ferromagnetic bcc iron using the first principles linear response linear-muffin-tin-orbital method in the generalizedgradient approximation. The calculated phonon dispersion and phonon density of states, both at ambient and high pressures, show good agreement with inelastic neutron scattering data. We find the free energy as a function of volume and temperature, including both electronic excitations and phonon contributions, and we have derived various thermodynamic properties at high pressure and temperature. The thermal equation of state at ambient temperature agrees well with diamond-anvil-cell measurements. We have performed detailed investigations on the behavior of various thermal equation of state parameters, such as the bulk modulus K, the thermal expansivity α, the Anderson-Grüneisen parameter δ T , the Grüneisen ratio γ, and the heat capacity C V as function of temperature and pressure. A detailed comparison has been made with available experimental measurements, as well as results from similar theoretical studies on nonmagnetic bcc Tantalum. PACS number(s): 05.70. Ce, 64.30.+t, 71.20.Be 1

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Section: Theoretical Methodsmentioning

confidence: 99%

Lattice dynamics and thermodynamics of bcc iron under pressure: First-principles linear response study

Sha

Cohen

2006

Phys. Rev. B

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“…However, the past few years have seen an increasing effort to apply DFT calculations to high-temperature solids and liquids of geological interest, using ab initio lattice dynamics or molecular-dynamics simulation (Alfè et al ( , 2002; Belonoshko et al (2000); Laio et al (2000); Stixrude et al (1997); Wasserman et al (1996); Brodholt et al (2002); Oganov et al (2001); Steinle-Neumann et al (2002)). Because dynamical DFT calculations demand large computer resources, a simplifying approximation known as the 'particle-in-cell' (PIC) method (Hirshfelder et al (1954); Holt and Ross (1970); ; Ree and Holt (1973); Westra and Cowley (1975); Cowley et al (1990)) has been used in some work on high-T , high-p solids, an important example being the very recent use of the PIC approximation to re-interpret the elastic anisotropy of the Earth's solid inner core (Steinle-Neumann et al (2001, 2002). However, the reliability of the PIC method has not gone unchallenged ) and conclusions based on it are not necessarily secure.…”

Section: Introductionmentioning

confidence: 99%

The particle-in-cell model for ab initio thermodynamics: implications for the elastic anisotropy of the Earth’s inner core

Gannarelli

Alfè

Gillan

2003

Physics of the Earth and Planetary Interiors

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We assess the quantitative accuracy of the particle-in-cell (PIC) approximation used in recent ab initio predictions of the thermodynamic properties of hexagonal-closepacked iron at the conditions of the Earth's inner core. The assessment is made by comparing PIC predictions for a range of thermodynamic properties with the results of more exact calculations that avoid the PIC approximation. It is shown that PIC gives very accurate results for some properties, but that it gives an unreliable treatment of anharmonic lattice vibrations. In addition, our assessment does not support recent PIC-based predictions that the hexagonal c/a ratio increases strongly with increasing temperature, and we point out that this casts doubt on a proposed re-interpretation of the elastic anisotropy of the inner core.

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“…The study of high temperature properties, however, is not reasonable with linearized augmented plane wave method as the simplified models of the electronic structure are unlikely to be successful for predicting the high temperature properties of transition metals due to the complicated many-body nature of the interactions. Wasserman et al [3] have recently studied the thermal properties of iron at high pressures and temperatures within the framework of shell model [7,8], which is well applicable above the Debye temperature where vibrational states are essentially fully populated. The model used by these workers is too good to predict the thermal properties of iron at high temperatures and pressures through heavy computational work that is involved in their calculation.…”

Section: Introductionmentioning

confidence: 99%

Analysis of thermal expansivity of iron (Fe) metal at ultra high temperature and pressure

Kandpal

Gupta

2007

Pramana - J Phys

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In the present investigation we have explained the thermal and compression properties of HCP iron (Fe) at high pressure with variable temperature (isobars) and at high temperature with variable pressure (isotherm). The usual Tait equation of state is modified by incorporating the effect of thermal pressure. The calculated values of pressure for different isotherms and isochors and thermal expansivity (α) as a function of both temperature and pressure have been compared with those values obtained by Isaak et al and Wasserman et al.

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Cell-cluster and self-consistent calculations for a model sodium chloride crystal

Cited by 24 publications

References 13 publications

Lattice dynamics and thermodynamics of bcc iron under pressure: First-principles linear response study

Lattice dynamics and thermodynamics of bcc iron under pressure: First-principles linear response study

The particle-in-cell model for ab initio thermodynamics: implications for the elastic anisotropy of the Earth’s inner core

Analysis of thermal expansivity of iron (Fe) metal at ultra high temperature and pressure

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