arXiv subjects

Marta Gałyńska

Publications and source records attributed to Marta Gałyńska.

9 recordsLinked to original sources

arXiv2026

A Flexible, Automated, and Basis-Set Insensitive Domain-Based Charge-Transfer Decomposition for Correlated Wavefunctions and its Application to Inter- and Intramolecular Cases

We present a flexible, automated, and basis-set insensitive domain-based charge-transfer (CT) decomposition framework that can be combined with any CI-type excited-state wavefunction. Our approach is not based on excited-state densities and allows the excited-state character to be dissected into local and domain-based CT excitations and measures the individual contributions to each excited state. To guarantee a broad applicability, we introduce two domain-accumulation strategies to translate hole-particle substitutions to domain-domain excitations: a strict domain partitioning and a weighted approach suitable for small molecules and a large number of domains. The performance of both schemes is assessed for inter- and intramolecular CT excitations and various basis sets using EOM-CCSD and its simplified counterpart EOM-pCCD+S. Most importantly, the CT character is, to a large extent, basis-set independent, and both domain-accumulation schemes give consistent results. Overall, our framework provides a robust CT analysis and a domain resolution of the excitation character for a variety of computational setups and excited-state models.

physics.chem-ph↗

arXiv2025

Localised and Delocalised Charge Distribution in a Diamine Cation and Rydberg Excited State: A Challenging Test for Density Functionals

The balance between localised and delocalised electron distribution in the N,N'-dimethylpiperazine (DMP) molecule in the 3s Rydberg excited state and in the fully ionised DMP$^+$ provides a valuable test of density functionals, in particular the weight of Fock exchange (FE) in hybrid functionals and the scaling of explicit orbital-based self-interaction correction (SIC) applied to less elaborate functionals. We present results of calculations using density functionals of all rungs of Jacob's ladder, ranging from LDA to the DM21 machine learned local hybrid as well as double hybrids. For DMP$^+$, the commonly used hybrid functionals, such as PBE0(.25) with FE weight of 0.25, as well as PBE0(.32) with a weight of 0.32 only produce the more delocalised charge. The latter mimics the DM21 energy surface well. However, hybrid functionals with stronger FE, such as BHLYP and PBE0(.50) as well as some double hybrid functionals, also produce local energy minima corresponding to localised charge. When full SIC is applied to the PBE functional, an energy surface analogous to hybrid functionals with FE weight of 0.50 is obtained, while the scaling of SIC by 0.50, which has previously been shown to give improved atomisation energy and band gap of solids, only produces the more delocalised charge. For the 3s Rydberg excited state of DMP, two types of configurations with a localised hole are obtained in calculations using the PBE0(.32) functional, in addition to the delocalised hole, but only the latter is found with the PBE functional, showing that a significant reduction of the self-interaction error is needed in order to obtain agreement between density functional calculations and experimental measurements of the Rydberg state

physics.chem-ph↗

arXiv2024

Changing the paradigm in f-containing cold molecules: the impact of spin-orbit coupling and f-d transitions on quasi-bound vibrational states

Present-day state-of-the-art ab initio many-body calculations on f-block containing cold molecules heavily focus on perturbative approaches for spin-orbit coupling and exclude a substantial part of the atomic transitions in the $f$- and $d$-shell. Here, we demonstrate the cruciality of a proper relativistic treatment of the $f$- and $d$-shell in Yb-containing diatomics and the inclusion of $f\rightarrow d$ transitions to obtain physically sound elastic scatterings and pre-dissociation lifetimes. We focus on state-of-the-art relativistic many-body calculations for the Yb atom's ground- and excited-state and the YbLi$^+$ potential energy surface. For that purpose, we exploit various quantum many-body methods, namely a spin-free and four-component implementation of the coupled cluster singles and doubles (CCSD) model and its equation of motion extensions, spin-free complete active space self-consistent field, and internally contracted multi-reference (MR) configuration interaction approaches, and spin-free MRCCSD with a perturbative and full triples correction. We oppose scalar relativistic calculations to four-component variants to support the reliability of our EOM-CCSD study and shed new light on the interplay between these systems' spin-orbit coupling and the proper treatment of relativistic effects. Most importantly, we observe a significant shift in the electronic spectra of the $f\rightarrow d$ excitation block. We also provide new reference potential energy surfaces for ground and excited states for which theoretically sound elastic scattering and pre-dissociation lifetimes are calculated.

physics.atom-ph↗

arXiv2024

Exploring electron affinities, LUMO energies, and band gaps with electron-pair theories

We introduce the electron attachment equation-of-motion pair coupled cluster doubles (EA-EOM-pCCD) ansatz, which allows us to inexpensively compute electron affinities, energies of unoccupied orbitals, and electron attachment spectra. We assess the accuracy of EA-EOM-pCCD for a representative data set of organic molecules for which experimental data is available, as well as the electron attachment process in uranyl dichloride. EA-EOM-pCCD provides more reliable energies for the LUMO than its ionization potential EOM counterpart for the HOMO. The advantage of EA-EOM-pCCD is demonstrated for rylene and rylene diimide units of different chain lengths, where the differences between theoretical and experimental EAs approach chemical accuracy.

physics.chem-ph↗

arXiv2024

Delving into the Catalytic Mechanism of Molybdenum Cofactors: A Novel Coupled Cluster Study

In this work, we use modern electronic structure methods to model the catalytic mechanism of different variants of the molybdenum cofactor (Moco). We investigate the dependence of various Moco model systems on structural relaxation and the importance of environmental effects for five critical points along the reaction coordinate with the DMSO and NO$_3^-$ substrates. Furthermore, we scrutinize the performance of various coupled-cluster approaches for modeling the relative energies along the investigated reaction paths, focusing on several pair coupled cluster doubles (pCCD) flavors and conventional coupled cluster approximations. Moreover, we elucidate the Mo--O bond formation using orbital-based quantum information measures, which highlight the flow of $σ_{\rm M-O}$ bond formation and $σ_{\rm N/S-O}$ bond breaking. Our study shows that pCCD-based models are a viable alternative to conventional methods and offer us unique insights into the bonding situation along a reaction coordinate. Finally, this work highlights the importance of environmental effects or changes in the core and, consequently, in the model itself to elucidate the change in activity of different Moco variants.

physics.chem-ph↗

arXiv2024

Benchmarking ionization potentials from pCCD tailored coupled cluster models

The ionization potential (IP) is an important parameter providing essential insights into the reactivity of chemical systems. IPs are also crucial for designing, optimizing, and understanding the functionality of modern technological devices. We recently showed that limiting the CC ansatz to the seniority-zero sector proves insufficient in predicting reliable and accurate ionization potentials within an IP equation-of-motion coupled-cluster formalism. Specifically, the absence of dynamic correlation in the seniority-zero pair coupled cluster doubles (pCCD) model led to unacceptably significant errors of approximately 1.5 eV. In this work, we aim to explore the impact of dynamical correlation and the choice of the molecular orbital basis (canonical vs. localized) in CC-type methods targeting 201 ionized states in 41 molecules. We focus on pCCD-based approaches as well as the conventional IP-EOM-CCD and IP-EOM-CCSD. Their performance is compared to the CCSDT equivalent and experimental reference data. Our statistical analysis reveals that all investigated frozen-pair coupled cluster methods exhibit similar performance, with differences in errors typically within chemical accuracy (1 kcal/mol or 0.05 eV). Notably, the effect of the molecular orbital basis, such as canonical Hartree-Fock or natural pCCD-optimized orbitals, on the IPs is marginal if dynamical correlation is accounted for. Our study suggests that triple excitations are crucial in achieving chemical accuracy in IPs when modeling electron detachment processes with pCCD-based methods.

physics.chem-ph↗

arXiv2023

Accelerating Pythonic coupled cluster implementations: a comparison between CPUs and GPUs

We scrutinize how to accelerate the bottleneck operations of Pythonic coupled cluster implementations performed on a \texttt{NVIDIA} Tesla V100S PCIe 32GB (rev 1a) Graphics Processing Unit (GPU). The \texttt{NVIDIA} Compute Unified Device Architecture (CUDA) API is interacted with via \texttt{CuPy}, an open-source library for Python, designed as a \texttt{NumPy} drop-in replacement for GPUs. The implementation uses the Cholesky linear algebra domain and is done in {PyBEST}, the Pythonic Black-box Electronic Structure Tool -- a fully-fledged modern electronic structure software package. Due to the limitations of Video Memory (VRAM), the GPU calculations must be performed batch-wise. Timing results of some contractions containing large tensors are presented. The \texttt{CuPy} implementation leads to factor 10 speed-up compared to calculations on 36 CPUs. Furthermore, we benchmark several Pythonic routines for time and memory requirements to identify the optimal choice of the tensor contraction operations available. Finally, we compare an example CCSD and pCCD-LCCSD calculation performed solely on CPUs to their CPU--GPU hybrid implementation. Our results indicate a significant speed-up (up to a factor of 16 regarding the bottleneck operations) when offloading specific contractions to the GPU using \texttt{CuPy}.

physics.chem-ph↗

arXiv2023

Geminal-based strategies for modeling large building blocks of organic electronic materials

We elaborate on unconventional electronic structure methods based on geminals and their potential to advance the rapidly developing field of organic photovoltaics (OPV). Specifically, we focus on the computational advantages of geminal-based methods over standard approaches and identify the critical aspects of OPV development. Examples are reliable and efficient computations of orbital energies, electronic spectra, and van-der-Waals interactions. Geminal-based models can also be combined with quantum embedding techniques and a quantum information analysis of orbital interactions to gain a fundamental understanding of the electronic structures and properties of realistic OPV building blocks. Furthermore, other organic components present in, for instance, dye-sensitized solar cells (DSSC) represent another promising scope of application. Finally, we provide numerical examples predicting the properties of a small building block of OPV components and two carbazole-based dyes proposed as possible DSSC sensitizers.

physics.chem-ph↗

arXiv2023

Benchmarking ionization potentials from the simple pCCD model

The electron-detachment energy is measured by its ionization potential (IP). As a result, it is a fundamental observable and important molecular electronic signature in photoelectron spectroscopy. A precise theoretical prediction of electron-detachment energies or ionization potentials is essential for organic optoelectronic systems like transistors, solar cells, or light-emitting diodes. In this work, we benchmark the performance of the recently presented IP variant of the equation-of-motion pair coupled cluster doubles (IP-EOM-pCCD) model to determine IPs. Specifically, the predicted ionization energies are compared to experimental results and higher-order coupled cluster theories based on statistically assessing 201 electron-detached states of 41 organic molecules for three different molecular orbital basis sets and two sets of particle-hole operators. While IP-EOM-pCCD features a reasonable spread and skewness of ionization energies, its mean error and standard deviation deviate up to 1.5 eV from reference data. Our study, thus, highlights the importance of dynamical correlation to reliably predict IPs from a pCCD reference function in small organic molecules.

physics.chem-ph↗