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arXiv · 2610.11767

Optical absorption spectra from the $GW$-Bethe-Salpeter framework for thousands of atoms

Maximilian Graml·Ritaj Tyagi·Rémi Pasquier·Štěpán Marek·Jan Wilhelm
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Abstract

The frequency-dependent absorption and emission of light determine the colors of matter and underpin today's technologies, from solar cells to light-emitting diodes. Predicting optical properties from first principles remains a computational challenge, especially for large and disordered systems. The $GW$ plus Bethe-Salpeter equation ($GW$-BSE) approach provides predictive accuracy for optical properties, but conventional implementations become costly as system size grows. Here, we present a $GW$-BSE framework combining real-time propagation, atom-centered basis sets, and a locally optimized real-space resolution of the identity. The cost of each propagation step scales quadratically with system size and roughly equals the cost of one self-consistent-field iteration in a density-functional calculation with a semilocal functional. This computational efficiency allows us to calculate the absorption spectrum of a nanographene containing 4616 atoms and opens a path toward routine calculations of optical properties for large disordered systems.

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Maximilian Graml, Ritaj Tyagi, Rémi Pasquier, Štěpán Marek, Jan Wilhelm. 2026-10-08. Optical absorption spectra from the $GW$-Bethe-Salpeter framework for thousands of atoms. https://arxiv.org/abs/2610.11767

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