New ab initio methods

Funded by The ERC Starting Grant of Ion Errea: Discovery and Characterization of Hydrogen-Based High-Temperature Superconductors (SuperH).

Software

Vibrational properties are crucial to describe the structural, thermodynamic, and transport properties of materials. The standard harmonic approximation assumes that ions in solids are placed at the minima of the Born-Oppenheimer potential and vibrate around these positions with phonon frequencies determined by the second-order derivatives of the potential. This picture is classical and neglects that ions are quantum objects that need to be described with a wave function. Moreover, phonon frequencies in this approach are temperature-independent and do not decay, which are intrinsic failures of this approach.

We have developed and continue developing the Stochastic Self-Consistent Harmonic Approximation (SSCHA) code that overcomes these limits. The SSCHA is a variational non-perturbative method that can calculate structural, vibrational, transport, and spectral properties of materials fully including quantum and thermal fluctuations as well as all anharmonic terms.  

Since part of the work we do is focused on the prediction of the critical temperature of superconductors, we have a particular interest on the ab initio calculation of the electron-phonon interaction. We work on new methods that go beyond the standard linear approach.

People involved in this line of research

  • Ion Errea

    Group leader
  • Đorđe Dangić

    Postdoc
  • Josu Diego

    PhD student
  • Yuewen Fang

    Postdoc
  • Diego Martínez Gutiérrez

    Postdoc

Publications in this research line

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

Lorenzo Monacelli, Raffaello Bianco, Marco Cherubini, Matteo Calandra, Ion Errea and Francesco Mauri
Journal of Physics: Condensed Matter 33, 363001 (2021)

Pressure and stress tensor of complex anharmonic crystals within the stochastic self-consistent harmonic approximation

Lorenzo Monacelli, Ion Errea, Matteo Calandra and Francesco Mauri
Physical Review B 97, 214101 (2018)

Approaching the strongly anharmonic limit with ab initio calculations of materials’ vibrational properties – a colloquium

Ion Errea
European Physical Journal B 89, 237 (2016)

First-principles calculations of phonon frequencies, lifetimes, and spectral functions from weak to strong anharmonicity: The example of palladium hydrides

Lorenzo Paulatto, Ion Errea, Matteo Calandra and Francesco Mauri
Physical Review B 91, 054304 (2015)

Presioak elementu eta aleazio sinpleetan induzitutako konplexutasunaren azterketa lehen-printzipioetan oinarritutako kalkuluen bidez

Ion Errea
PhD thesis (2011)

Pressure induced complexity in simple elements and alloys from first-principles calculations

Ion Errea
PhD thesis (2011)

Anharmonic Stabilization of the High-Pressure Simple Cubic Phase of Calcium.

Ion Errea, Bruno Rousseau and Aitor Bergara
Physical Review Letters 106, 165501 (2010)