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Reliable computational methodologies and basis sets for modeling x-ray spectra are essential for extracting and interpreting electronic and structural information from experimental x-ray spectra. In particular, the trade-off between numerical accuracy and computational cost due to the size of the basis set is a major challenge, since molecular orbitals undergo extreme relaxation in the core-hole state. To gain clarity on the changes in electronic structure induced by the formation of a core-hole, the use of sufficiently flexible basis for expanding the orbitals, particularly for the core region, has been shown to be essential. This work focuses on the refinement of core-hole ionized state calculations using the equation-of-motion coupled cluster family of methods through an extensive analysis on the effectiveness of “hybrid” and mixed basis sets. In this investigation, we utilize the CVS-EOMIP-CCSD method in combination and construct hybrid basis sets piecewise from readily available Dunning’s correlation consistent basis sets in order to calculate x-ray ionization energies (IEs) for a set of small gas phase molecules. Our results provide insights into the impact of basis sets on the CVS-EOMIP-CCSD calculations of K-edge IEs of first-row p-block elements. These insights enable us to understand more about the basis set dependence of the core IEs computed and allow us to establish a protocol for deriving reliable and cost-effective theoretical estimates for computing IEs of small molecules containing such elements.
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Fast and Efficient Evaluation of Integrals Arising in Iso-geometric Analysis
Integral equation based analysis of scattering (both acoustic and electromagnetic) is well known and has been studied for several decades. Analysis typically proceeds along the following lines: representation of the geometry using a collection of triangles, representation of physics using piecewise constant basis function defined on each triangle, and then solving the resulting discrete system. In the past few decades, this area has seen several improvements in algorithms that reduce the computational complexity of analysis. But, as we delve into higher order isogeometric analysis (IGA), these algorithms are bogged down by the cost of integration. In this paper, we seek to address this challenge. Our candidate for modeling geometry and physics are subdivision basis sets. The order of these basis sets is sufficiently high to make the challenge apparent. We will present a methodology to ameliorate the cost for both acoustic and electromagnetic integral equations and demonstrate its efficacy.
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- Award ID(s):
- 1725278
- PAR ID:
- 10182400
- Date Published:
- Journal Name:
- 2020 International Symposium on Antennas and Propagation
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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