In this research, we’ve developed a powerful and efficient method for simulating X-ray photoelectron spectra (XPS), a technique used to study materials at the atomic level. Our approach, based on a second quantization-based theory called multireference algebraic diagrammatic construction (MR-ADC), and allows for incredibly detailed simulations of molecules with thousands of orbitals.
New Efficiency Boundaries for MR-ADC
- Efficiency: We’ve optimized the MR-ADC method using spin adaptation, automatic code generation, and density fitting techniques. This allows us to handle much larger and more complex molecules than previously possible.
- New Open-Source Framework: The new efficient framework, called Prism, includes efficient CPU parallelization and memory management and paves a promising way to develop new multireference methods based on the Dyall Hamiltonian.
- Accuracy: Our simulations incorporate static and dynamic correlations within the molecule, leading to highly accurate predictions that closely match real-world XPS measurements.
- Time-resolved XPS: This method can even be used to simulate how XPS spectra change during a molecule’s transformation, providing valuable insights into dynamic processes.
Applications
We’ve successfully applied our method to simulate the XPS spectra of various molecules, including ferrocene complexes and the time-resolved photoionization of azobenzene isomers. The core states simulations using the advanced MR-ADC(2)-X method showed excellent agreement with experimental data and presented useful insights for future experiments.
Moving Forward
This research is the first step towards a new generation of efficient and accurate tools for multireference simulations of spectroscopic methods. Our future work will focus on further refining these methods and applying them to a wider range of molecules.
de Moura, C. E. V., Sokolov, A. Yu. Efficient Spin-Adapted Implementation of Multireference Algebraic Diagrammatic Construction Theory. I. Core-Ionized States and X-Ray Photoelectron Spectra. Phys. Chem. A (2024). [Link]