Self-consistent-screening calculation of interatomic force constants and phonon dispersion curves from first principles

Fast, efficient, and accurate dielectric screening using a local real-space approach

Various many-body perturbation theory techniques for calculating electron behavior rely on W, the screened Coulomb interaction. Computing W requires complete knowledge of the dielectric response of the electronic system, and the fidelity of the calculated dielectric response limits the reliability of predicted electronic and structural properties. As a simplification, calculations often begin with the random-phase approximation (RPA). However, even RPA calculations are costly and scale poorly, typically as N ⁴ (N representing the system size). A local approach has been shown to be efficient while maintaining accuracy for screening core-level excitations [Ultramicroscopy 106, 986 (2006)]. We extend this method to valence-level excitations. We present improvements to the accuracy and execution of this scheme, including reconstruction of the all-electron character of the pseudopotential-based wave functions, improved N ² log N scaling, and a parallelized implementation. We discuss applications to Bethe-Salpeter equation calculations of core and valence spectroscopies.

Coupling First-Principles Calculations of Electron-Electron and Electron-Phonon Scattering, and Applications to Carbon-Based Nanostructures

We report first-principles calculations of electronic gaps, lifetimes, and photoelectron spectra of a series of molecules, performed by efficiently combining the computation of electron-electron and electron-phonon self-energies. The dielectric matrix is represented in terms of dielectric eigenpotentials, utilized for both the calculation of G₀ W₀ quasi-particle energies and the diagonalization of the dynamical matrix; virtual electronic states are never explicitly computed and all self-energies are evaluated over the full frequency spectrum. Our formulation enables electronic structure calculations at the many-body perturbation theory level, inclusive of electron-phonon coupling, for systems with hundreds of electrons.

Linear response calculations of lattice dynamics in strongly correlated systems

We introduce a new linear response method to study the lattice dynamics of materials with strong correlations. It is based on a combination of dynamical mean field theory of strongly correlated electrons and the local density functional theory of electronic structure. We apply the method to study the phonon dispersions of Mott insulators NiO and MnO in their paramagnetic insulating state not accessible by local density functionals. Our results are in good agreement with experiment.