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We present the theory and implementation of a core-valence separated similarity transformed EOM-CCSD (STEOM-CCSD) method for K-edge core excitation spectra. The method can select an appropriate active space using CIS natural orbitals and…

Chemical Physics · Physics 2020-11-03 Santosh Ranga , Achintya Kumar Dutta

We present a new theoretical approach for the simulations of X-ray photoelectron spectra of strongly correlated molecular systems that combines multireference algebraic diagrammatic construction theory (MR-ADC) [J. Chem. Phys., 2018, 149,…

Chemical Physics · Physics 2022-05-31 Carlos E. V. de Moura , Alexander Yu. Sokolov

We develop and demonstrate how to use the GUGA-based MRCISD with Core-Valence Separation approximation (CVS) to compute the core-excited states. Firstly, perform a normal SCF or valence MCSCF calculation to optimize the molecular orbitals.…

Computational Physics · Physics 2023-11-16 Qi Song , Baoyuan Liu , Junfeng Wu , Wenli Zou , Yubin Wang , Bingbing Suo , Yibo Lei

We present an efficient implementation of the second-order two-component relativistic core-valence-separated algebraic diagrammatic construction method (CVS-ADC(2)) for core-excitation calculations. The approach employs state-averaged…

Chemical Physics · Physics 2026-05-01 Somesh Chamoli , Sudipta Chakraborty , Xubo Wang , Achintya Kumar Dutta

The phenomenon of orbital relaxation upon excitation of core electrons is a major problem in the linear-response treatment of core-hole spectroscopies. Rather than addressing relaxation through direct dynamical correlation of the excited…

Chemical Physics · Physics 2025-03-26 Megan Simons , Devin A. Matthews

L-edge X-ray absorption spectra for first-row transition metal complexes are obtained from relativistic equation-of-motion singles and doubles coupled-cluster (EOM-CCSD) calculations that make use of the core-valence separation (CVS)…

This work examines the accuracy of different many-body methods for the calculations of parity violating electric dipole ($E1_{\text{PV}}$) amplitudes in atomic systems. In the last decade many different groups claim to achieve its accuracy…

Atomic Physics · Physics 2024-06-27 A. Chakraborty , B. K. Sahoo

In this work, two approaches for simulating X-ray absorption (XA) spectra with the complete active space self-consistent field (CASSCF) linear response (LR) method are introduced. The first approach employs the well-known core-valence…

Chemical Physics · Physics 2022-03-10 Benjamin Helmich-Paris

The $GW$ approximation has been recently gaining popularity among the method for simulating molecular core-level X-ray photoemission spectra. Traditionally, $GW$ core-level binding energies have been computed using either the cc-pV$n$Z or…

Chemical Physics · Physics 2022-07-13 Daniel Mejia-Rodriguez , Alexander Kunitsa , Edoardo Aprà , Niranjan Govind

We investigate the use of orbital-optimized references in conjunction with single-reference coupled-cluster theory with single and double substitutions (CCSD) for the study of core excitations and ionizations of 18 small organic molecules,…

We report the development and benchmark of multireference algebraic diagrammatic construction theory (MR-ADC) for the simulations of core-excited states and X-ray absorption spectra (XAS). Our work features an implementation that…

Chemical Physics · Physics 2024-01-23 Ilia M. Mazin , Alexander Yu. Sokolov

We present a methodology for model evaluation and selection where the sampling mechanism violates the i.i.d. assumption. Our methodology involves a formulation of the bias between the standard Cross-Validation (CV) estimator and the mean…

Methodology · Statistics 2025-03-14 Oren Yuval , Saharon Rosset

We demonstrate excitation-manifold resolved polarisation characterisation of continuous-variable (CV) quantum states. In contrast to traditional characterisation of polarisation that is based on the Stokes parameters, we experimentally…

Quantum Physics · Physics 2013-04-24 Christian Kothe , Lars Skovgaard Madsen , Ulrik Lund Andersen , Gunnar Björk

We present a new approach for simulating X-ray absorption spectra based on linear-response density cumulant theory (LR-DCT) [A. V. Copan and A. Yu. Sokolov, J. Chem. Theory Comput., 2018, 14, 4097 - 4108]. Our new method combines the…

Chemical Physics · Physics 2019-06-03 Ruojing Peng , Andreas V. Copan , Alexander Yu. Sokolov

We systematically investigate the underlying relations among different levels of approximation for simulating electronic de-excitations, with a focus on modeling X-ray emission spectroscopy (XES). Using Fermi's golden rule and explicit…

Materials Science · Physics 2022-08-31 Subhayan Roychoudhury , Leonardo A. Cunha , Martin Head-Gordon , David Prendergast

We develop an approximation formula for the cross-validation error (CVE) of a sparse linear regression penalized by $\ell_1$-norm and total variation terms, which is based on a perturbative expansion utilizing the largeness of both the data…

Methodology · Statistics 2017-12-13 Tomoyuki Obuchi , Shiro Ikeda , Kazunori Akiyama , Yoshiyuki Kabashima

K-fold cross-validation (CV) with squared error loss is widely used for evaluating predictive models, especially when strong distributional assumptions cannot be taken. However, CV with squared error loss is not free from distributional…

Methodology · Statistics 2021-08-10 Assaf Rabinowicz , Saharon Rosset

A numerical security proof technique is used to analyse the security of continuous-variable quantum key distribution (CV-QKD) protocols with phase-shift keying modulation against collective attacks in the asymptotic limit. We argue why it…

Quantum Physics · Physics 2022-10-18 Florian Kanitschar , Christoph Pacher

We present a detailed convergence analysis for an operator splitting scheme proposed in [C. Liu et al.,J. Comput. Phys., 436, 110253, 2021] for a reaction-diffusion system with detailed balance. The numerical scheme has been constructed…

Numerical Analysis · Mathematics 2021-05-21 Chun Liu , Cheng Wang , Yiwei Wang , Steven M. Wise

Reconciliation is an essential procedure for continuous-variable quantum key distribution (CV-QKD). As the most commonly used reconciliation protocol in short-distance CV-QKD, the slice error correction (SEC) allows a system to distill more…

Quantum Physics · Physics 2021-06-17 Xuan Wen , Qiong Li , Haokun Mao , Xiaojun Wen , Nan Chen
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