All-Electron Dynamical Bethe-Salpeter Equation Method Developed for Extended Systems
Researchers have formulated and implemented an all-electron numerical atom-centered orbital (NAO) approach for solving the dynamical Bethe-Salpeter equation (BSE) in extended systems, validated through application to naphthalene molecular crystal. The work addresses a longstanding limitation of the widely used static approximation to the screened Coulomb interaction kernel, which breaks down when excitonic effects are strong. This advance could improve the accuracy of first-principles calculations of electronic excitations in materials where exciton binding energies are large.
The Bethe-Salpeter equation (BSE) is the standard many-body Green's function approach for describing particle-hole (exciton) interactions in electronic excitations, but it is conventionally solved under a static approximation to the screened Coulomb interaction. This approximation becomes unreliable in systems with significant excitonic character, where dynamical screening effects are non-negligible. Solving the dynamical BSE for extended systems has remained computationally challenging, particularly when combined with GW calculations for quasiparticle energies, due to the need for dense Brillouin zone integration. In this work, the authors adapt a plane-wave-based effective dielectric function method to work with atom-centered orbital basis functions, implementing it within an existing all-electron NAO-based BSE@GW framework for extended systems. The method is validated and then applied to the molecular crystal naphthalene using dynamical BSE@G0W0 calculations, demonstrating its practical applicability to real materials. The approach is expected to be particularly valuable for organic molecular crystals and other systems where strong excitonic effects render the static approximation inadequate.
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- arXiv physicsCenter
Efficient analytic continuation approach to Bethe-Salpeter excitation spectra in selected energy windows
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