Exact Two-Component TDDFT with Simple Two-Electron Picture-Change Corrections: X-ray Absorption Spectra Near L- and
Lukas Konecny1,2, Stanislav Komorovsky3, Jan Vicha4
1Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, UiT The Arctic University of Norway, N-9037Tromsø, Norway.
The Journal of Physical Chemistry. A
|February 1, 2023
Summary
This study introduces new two-component (2c) relativistic quantum-chemical methods, (e)amfX2C, for accurate X-ray absorption spectroscopy (XAS) calculations. These methods effectively model scalar and spin-orbit effects, offering computational savings over four-component approaches.
Area of Science:
- Quantum Chemistry
- Spectroscopy
- Relativistic Effects
Background:
- X-ray absorption spectroscopy (XAS) is a powerful technique for probing matter with high elemental and spatial sensitivity.
- Theoretical modeling of XAS is complex due to relativistic effects, particularly scalar (SC) and spin-orbit (SO) interactions near L and M absorption edges.
- While four-component (4c) calculations are accurate, there's a need for efficient two-component (2c) relativistic methods.
Purpose of the Study:
- To develop and validate accurate and computationally efficient 2c relativistic methods for XAS calculations.
- To investigate the impact of picture-change (PC) corrections on relativistic effects in XAS.
- To compare the performance of new (e)amfX2C methods against traditional 1eX2C and accurate 4c calculations.
Main Methods:
- Implementation of two-component (2c) relativistic Hamiltonians, (e)amfX2C, within a linear eigenvalue and damped response time-dependent density functional theory (TDDFT) framework.
- Inclusion of scalar (SC) and spin-orbit (SO) two-electron and exchange-correlation picture-change (PC) effects in the (e)amfX2C Hamiltonians.
- Application to L- and M-edge XAS spectra of transition metal and actinide compounds.
Main Results:
- The commonly used one-electron X2C (1eX2C) Hamiltonian significantly overestimates SO splittings due to the absence of PC corrections.
- The proposed (e)amfX2C Hamiltonians accurately reproduce spectral features, including shape, position, and SO splitting, matching 4c reference calculations.
- These 2c methods provide substantial computational savings compared to 4c approaches.
Conclusions:
- The (e)amfX2C PC correction models offer reliable and computationally efficient relativistic 2c quantum-chemical approaches for XAS modeling.
- These methods are suitable for accurately calculating XAS spectra, especially for systems with significant relativistic effects.
- The study highlights the importance of PC corrections for accurate relativistic calculations in XAS.
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