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We present a fully numerical framework for the optimization of molecule-specific quantum chemical basis functions within the quantics tensor train format using a finite-difference scheme. The optimization is driven by solving the…

Chemical Physics · Physics 2025-06-12 Paul Haubenwallner , Matthias Heller

General method is suggested to find non-relativistic and relativistic matrix elements of one- and two-electron operators for any number of open shells in atom, requiring neither coefficients of fractional parentage nor unit tensors. It is…

Atomic Physics · Physics 2007-05-23 G. Gaigalas , Z. Rudzikas

Magnetic materials are typically described in terms of the Heisenberg model, which provides an accurate account of thermodynamic properties when combined with first principles calculations. This approach is usually based on an energy…

Materials Science · Physics 2020-12-04 Daniele Torelli , Thomas Olsen

Using the recently developed Nth-order muffin-tin-orbital (NMTO) based downfolding technique we revisit the electronic properties of half-metallic ferromagnets, the semi-Heusler NiMnSb and rutile CrO2. The NMTO Wannier orbitals for the Mn-d…

Strongly Correlated Electrons · Physics 2007-05-23 A. Yamasaki , L. Chioncel , A. I. Lichtenstein , O. K. Andersen

The magnetic properties of the transition metal monoxides MnO and NiO are investigated at equilibrium and under pressure via several advanced first-principles methods coupled with Heisenberg Hamiltonian MonteCarlo. The comparative…

Strongly Correlated Electrons · Physics 2015-05-28 T. Archer , C. D. Pemmaraju , S. Sanvito , C. Franchini , J. He , A. Filippetti , P. Delugas , D. Puggioni , V. Fiorentini , R. Tiwari , P. Majumdar

We introduce a machine-learning (ML) framework for high-throughput benchmarking of diverse representations of chemical systems against datasets of materials and molecules. The guiding principle underlying the benchmarking approach is to…

Machine Learning · Computer Science 2021-12-07 Carl Poelking , Felix A. Faber , Bingqing Cheng

A singularly perturbed linear system of second order ordinary differential equations of reaction-diffusion type with given boundary conditions is considered. The leading term of each equation is multiplied by a small positive parameter.…

Numerical Analysis · Mathematics 2010-04-06 M. Paramasivam , S. Valarmathi , J. J. H. Miller

We discuss advanced statistical methods to improve parameter estimation of nuclear models. In particular, using the Liquid Drop Model for nuclear binding energies, we show that the area around the global $\chi^2$ minimum can be efficiently…

Nuclear Theory · Physics 2018-11-26 M. Shelley , P. Becker , A. Gration , A. Pastore

Joint diagonalization, the process of finding a shared set of approximate eigenvectors for a collection of matrices, arises in diverse applications such as multidimensional harmonic analysis or quantum information theory. This task is…

Optimization and Control · Mathematics 2025-02-12 Erik Troedsson , Marcus Carlsson , Herwig Wendt

Quantum mechanics/molecular mechanics (QM/MM) hybrid models allow one to address chemical phenomena in complex molecular environments. Whereas this modeling approach can cope with a large system size at moderate computational costs, the…

Computational Physics · Physics 2023-01-10 Katja-Sophia Csizi , Markus Reiher

The IMPRESSION (Intelligent Machine PREdiction of Shift and Scalar Information Of Nuclei) machine learning system provides an efficient and accurate route to the prediction of NMR parameters from 3-dimensional chemical structures. Here we…

Sequential Monte Carlo samplers represent a compelling approach to posterior inference in Bayesian models, due to being parallelisable and providing an unbiased estimate of the posterior normalising constant. In this work, we significantly…

Methodology · Statistics 2022-11-24 Samuel Duffield , Sumeetpal S. Singh

In this paper, we propose a unified framework, the Hessian discretisation method (HDM), which is based on four discrete elements (called altogether a Hessian discretisation) and a few intrinsic indicators of accuracy, independent of the…

Numerical Analysis · Mathematics 2018-08-28 Jérôme Droniou , Bishnu P. Lamichhane , Devika Shylaja

Differentiable programming is revolutionizing computational science by enabling automatic differentiation (AD) of numerical simulations. While first-order gradients are well-established, second-order derivatives (Hessians) for implicit…

Computational Engineering, Finance, and Science · Computer Science 2025-05-20 Tianju Xue

One of the primary challenges in quantum chemistry is the accurate modeling of strong electron correlation. While multireference methods effectively capture such correlation, their steep scaling with system size prohibits their application…

We describe the application of model inference based on reference priors to two concrete examples in high energy physics: the determination of the CKM matrix parameters rhobar and etabar and the determination of the parameters m_0 and m_1/2…

High Energy Physics - Phenomenology · Physics 2011-07-15 Maurizio Pierini , Harrison Prosper , Sezen Sekmen , Maria Spiropulu

A new approach is presented to improve the performance of semiempirical quantum mechanical (SQM) methods in the description of noncovalent interactions. To show the strategy, the PM6 Hamiltonian was selected, although, in general, the…

This paper focusses on the optimal control problems governed by fourth-order linear elliptic equations with clamped boundary conditions in the framework of the Hessian discretisation method (HDM). The HDM is an abstract framework that…

Numerical Analysis · Mathematics 2022-12-14 Devika Shylaja

A common approach to model complex chemistry in numerical simulations is via post-processing of existing magneto-hydrodynamic simulations, relying on computing the evolution of chemistry over the dynamic history of a subset of particles…

Solar and Stellar Astrophysics · Physics 2021-07-07 Simón Ferrada-Chamorro , Alessandro Lupi , Stefano Bovino

High fidelity models used in many science and engineering applications couple multiple physical states and parameters. Inverse problems arise when a model parameter cannot be determined directly, but rather is estimated using (typically…

Optimization and Control · Mathematics 2020-12-30 Isaac Sunseri , Joseph Hart , Bart van Bloemen Waanders , Alen Alexanderian