Dynamic-local-field approximation for the quantum solids

Etters, R. D.; Danilowicz, R.

doi:10.1103/physreva.9.1698

Cited by 16 publications

(7 citation statements)

References 19 publications

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“…It has been also argued 33 that structural properties of solids under pressure can be described rather accurately by a classical model for the lattice vibrations. The origin of this is similar to that described above for the decreasing effect of anharmonicity as P rises, since in this respect the actual description of the lattice vibrations by a classical or a quantum model becomes unimportant for solids under large pressures.…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, the improved accuracy of the QHA as pressure rises is not a particular merit of this approach, since the internal energy becomes dominated by the elastic energy and the actual description of the vibrational modes is not very relevant for thermodynamic properties. It has been also argued 33 that structural properties of solids under pressure can be described rather accurately by a classical model for the lattice vibrations. The origin of this is similar to that described above for the decreasing effect of anharmonicity as P rises, since in this respect the actual description of the lattice vibrations by a classical or a quantum model becomes unimportant for solids under large pressures.…”

Section: Bulk Modulusmentioning

confidence: 99%

“…32 It has been also argued that at high pressures, thermodynamic properties of solids can be well described by classical calculations, i.e., dealing with the atoms as classical oscillators in a given potential. 33 This seems to be at first sight contradictory with the fact that pressure induces a larger zero-point vibrational energy of the solid. These questions are indeed related with the ratio of the vibrational energy to the whole internal energy on one side, and with the size of the "intrinsic" anharmonicity (further than the QHA) of the lattice vibrations, on the other side.…”

Section: Introductionmentioning

confidence: 99%

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Rare-gas solids under pressure: A path-integral Monte Carlo simulation

Herrero

Ramı́rez

2005

Phys. Rev. B

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Rare-gas solids (Ne, Ar, Kr, and Xe) under hydrostatic pressure up to 30 kbar have been studied by path-integral Monte Carlo simulations in the isothermal-isobaric ensemble. Results of these simulations have been compared with available experimental data and with those obtained from a quasiharmonic approximation (QHA). This comparison allows us to quantify the overall anharmonicity of the lattice vibrations and its influence on several structural and thermodynamic properties of rare-gas solids. The vibrational energy increases with pressure, but this increase is slower than that of the elastic energy, which dominates at high pressures. In the PIMC simulations, the vibrational kinetic energy is found to be larger than the corresponding potential energy, and the relative difference between both energies decreases as the applied pressure is raised. The accuracy of the QHA increases for rising pressure.

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Section: Discussionmentioning

confidence: 99%

Section: Bulk Modulusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Rare-gas solids under pressure: A path-integral Monte Carlo simulation

Herrero

Ramı́rez

2005

Phys. Rev. B

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“…In this work we make the simplifying assumption that G may be represented by its spherical average, in which case it may be evaluated in precisely the same manner as in Ref. 11. Even with this approximation, the expectation value of the Hamiltonian still involves the solution of a series of 12-dimensional integrals.…”

Section: Methodsmentioning

confidence: 99%

Anisotropic contributions to the ground-state properties of solid para-H2

1978

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The local field approximation is modified so that the translational and rotational degrees of freedom of the He molecule are treated on an equal basis, when calculating the equation of state for solid para-H2. Near normal vapor pressure the anisotropies in the H2 pair interaction are found to make a negligible contribution to the binding energy and the equation of state, but that contribution increases with increasing pressure. However, the isotropic part of the potential plays the dominant role in determining the equation of state at all molar volumes investigated 3<-V<~22.65cm3/mole. At extremely high pressures the results tend toward previous findings that were based upon a frozen P42/mnm (y-N2) orientational structure.

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“…However, the relevant factor here is again (as for the QHA) the ratio of the vibrational energy to the whole internal energy of the solid. Since in this respect the lattice vibrations become less relevant as pressure rises, and eventually give a relatively small contribution to the free energy of the solid, their actual description by a classical or a quantum model becomes less important for solids under large pressures [98,99]. This is not necessarily true for spectro- squares [14], diamonds [16], triangles up [108], and triangles down [15].…”

Section: A Volumementioning

confidence: 99%

Path-integral simulation of ice VII: Pressure and temperature effects

Herrero

Ramı́rez

2015

Chemical Physics

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Effects of pressure and temperature on structural and thermodynamic properties of ice VII have been studied by using path-integral molecular dynamics (PIMD) simulations. Temperatures between 25 and 450 K, as well as pressures up to 12 GPa were considered. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. We analyze the pressure dependence of the molar volume, bulk modulus, interatomic distances, kinetic energy, and atomic delocalization at various temperatures. Results of PIMD simulations are compared with those derived from a quasi-harmonic approximation (QHA) of vibrational modes, which helps to assess the importance of anharmonic effects, as well as the influence of the different modes on the properties of ice VII. The accuracy of the QHA for describing this high-pressure phase decreases for rising temperature, but this approximation becomes more reliable as pressure grows, since anharmonicity becomes less relevant. Comparisons with low-pressure cubic ice are presented.Comment: 15 pages, 12 figure

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Dynamic-local-field approximation for the quantum solids

Cited by 16 publications

References 19 publications

Rare-gas solids under pressure: A path-integral Monte Carlo simulation

Rare-gas solids under pressure: A path-integral Monte Carlo simulation

Anisotropic contributions to the ground-state properties of solid para-H2

Path-integral simulation of ice VII: Pressure and temperature effects

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