Low scaling BSE implementation in the exciting code
Abstract
Solving the Bethe-Salpeter Equation (BSE) is essential for understanding excited-state systems, but often challenging to converge or even computationally prohibitive for large systems.We implement a matrix-free BSE solver leveraging Interpolative Separable Density Fitting (ISDF) to interpolate electron-hole interaction kernels together with the Lanczos algorithm for diagonalization, avoiding full matrix setup.The scaling of our implementation is bounded by 𝒪(𝑁 𝑜 𝑁 𝑢 𝑁 k log 𝑁 k ) and is thus a massive improvement over methods that set up the whole matrix, scaling with at least 𝒪((𝑁 𝑜 𝑁 𝑢 𝑁 k ) 3 ), where 𝑁 𝑜 and 𝑁 𝑢 are the numbers of occupied and unoccupied states, respectively, and 𝑁 k is the number k-points.
Fields of Study & Subjects
Advanced Software Engineering Methodologies
Distributed and Parallel Computing Systems
Software System Performance and Reliability
Publication details
- Journal / source
- The Journal of Open Source Software
- Publisher
- The Open Journal
- Volume
- 11
- Issue
- 118
- Pages
- 8866–8866
- Publication date
- 3 February 2026