The stochastic self-consistent harmonic approximation: calculating vibrational properties of materials with full quantum and anharmonic effects.

anharmonicity computational methods first-principles methods ionic fluctuations quantum effects stochastic self-consistent harmonic approximation

Journal

Journal of physics. Condensed matter : an Institute of Physics journal
ISSN: 1361-648X
Titre abrégé: J Phys Condens Matter
Pays: England
ID NLM: 101165248

Informations de publication

Date de publication:
13 Jul 2021
Historique:
received: 09 03 2021
accepted: 28 05 2021
pubmed: 29 5 2021
medline: 29 5 2021
entrez: 28 5 2021
Statut: epublish

Résumé

The efficient and accurate calculation of how ionic quantum and thermal fluctuations impact the free energy of a crystal, its atomic structure, and phonon spectrum is one of the main challenges of solid state physics, especially when strong anharmonicy invalidates any perturbative approach. To tackle this problem, we present the implementation on a modular Python code of the stochastic self-consistent harmonic approximation (SSCHA) method. This technique rigorously describes the full thermodynamics of crystals accounting for nuclear quantum and thermal anharmonic fluctuations. The approach requires the evaluation of the Born-Oppenheimer energy, as well as its derivatives with respect to ionic positions (forces) and cell parameters (stress tensor) in supercells, which can be provided, for instance, by first principles density-functional-theory codes. The method performs crystal geometry relaxation on the quantum free energy landscape, optimizing the free energy with respect to all degrees of freedom of the crystal structure. It can be used to determine the phase diagram of any crystal at finite temperature. It enables the calculation of phase boundaries for both first-order and second-order phase transitions from the Hessian of the free energy. Finally, the code can also compute the anharmonic phonon spectra, including the phonon linewidths, as well as phonon spectral functions. We review the theoretical framework of the SSCHA and its dynamical extension, making particular emphasis on the physical inter pretation of the variables present in the theory that can enlighten the comparison with any other anharmonic theory. A modular and flexible Python environment is used for the implementation, which allows for a clean interaction with other packages. We briefly present a toy-model calculation to illustrate the potential of the code. Several applications of the method in superconducting hydrides, charge-density-wave materials, and thermoelectric compounds are also reviewed.

Identifiants

pubmed: 34049302
doi: 10.1088/1361-648X/ac066b
doi:

Types de publication

Journal Article Review

Langues

eng

Sous-ensembles de citation

IM

Informations de copyright

Creative Commons Attribution license.

Auteurs

Lorenzo Monacelli (L)

Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy.

Raffaello Bianco (R)

Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia/San Sebastián, Spain.

Marco Cherubini (M)

Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy.
Center for Life NanoScience, Istituto Italiano di Tecnologia, Viale ReginaElena 291, 00161 Rome, Italy.

Matteo Calandra (M)

Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252 Paris, France.
Dipartimento di Fisica, Universitá di Trento, Via Sommarive 14, 38123 Povo, Italy.

Ion Errea (I)

Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia/San Sebastián, Spain.
Fisika Aplikatua Saila, Gipuzkoako Ingeniaritza Eskola, University of the Basque Country (UPV/EHU), Europa Plaza 1, 20018 Donostia/San Sebastián, Spain.
Donostia International Physics Center (DIPC), Manuel Lardizabal pasealekua 4, 20018 Donostia/San Sebastián, Spain.

Francesco Mauri (F)

Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy.

Classifications MeSH