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Related papers: $\mathbb{i}$CAS: Imposed Automatic Selection and L…

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We present our implementation autoCAS for fully automated multi-configurational calculations, which we also make available free of charge on our webpages. The graphical user interface of autoCAS connects a general electronic structure…

Chemical Physics · Physics 2019-12-03 Christopher J. Stein , Markus Reiher

We have developed and implemented a new ab initio code, CERES (Computational Emulator of Rare Earth Systems), completely written in C++11, which is dedicated to the efficient calculation of the electronic structure and magnetic properties…

Strongly Correlated Electrons · Physics 2017-10-02 Simone Calvello , Matteo Piccardo , Shashank V. Rao , Alessandro Soncini

We present the time-dependent complete-active-space self-consistent-field (TD-CASSCF) method to simulate multielectron dynamics in ultrafast intense laser fields from the first principles. While based on multiconfiguration expansion, it…

Atomic Physics · Physics 2018-04-24 Takeshi Sato , Yuki Orimo , Takuma Teramura , Oyunbileg Tugs , Kenichi L. Ishikawa

This paper introduces the methodology proposed by our group to model the biological soft tissues deformations and to couple these models with Computer-Assisted Surgical (CAS) applications. After designing CAS protocols that mainly focused…

In this work, we develop a new orbital optimization approach, perturbative Super-CI (Super-CIPT), for the two-component complete active space self-consistent field (2C-CASSCF) method. By variationally optimizing spinor orbitals and…

Chemical Physics · Physics 2026-03-04 Yang Guo , Achintya Kumar Dutta

A successful and commonly used ab initio method for the calculation of crystal field levels and magnetic anisotropy of lanthanide complexes consists of spin-adapted state-averaged CASSCF calculations followed by state interaction with…

Chemical Physics · Physics 2016-06-08 Willem Van den Heuvel , Simone Calvello , Alessandro Soncini

For many-body methods such as MCSCF and CASSCF, in which the number of one-electron orbitals are optimized and independent of basis set used, there are no problems with using plane-wave basis sets. However, for methods currently used in…

Computational Physics · Physics 2020-09-02 Eric J. Bylaska , Duo Song , Nicholas P. Bauman , Karol Kowalski , Daniel Claudino , Travis S. Humble

Density functional theory offers accurate structure prediction at acceptable computational cost, but commonly used approximations suffer from delocalization error; this results in inaccurate predictions of quantities such as energy band…

Materials Science · Physics 2022-08-17 Aaron Mahler , Jacob Z. Williams , Neil Qiang Su , Weitao Yang

Even when starting with a very poor initial guess, the iterative configuration interaction (iCI) approach can converge from above to full CI very quickly by constructing and diagonalizing a small Hamiltonian matrix at each…

Chemical Physics · Physics 2020-01-07 Ning Zhang , Wenjian Liu , Mark R. Hoffmann

Full configuration interaction (FCI) solvers are limited to small basis sets due to their expensive computational costs. An optimal orbital selection for FCI (OptOrbFCI) is proposed to boost the power of existing FCI solvers to pursue the…

Chemical Physics · Physics 2020-09-01 Yingzhou Li , Jianfeng Lu

Localized orbital-based quantum embedding, as originally formulated in the context of density matrix embedding theory (DMET), is revisited from the perspective of lattice density functional theory (DFT). An in-principle exact (in the sense…

Strongly Correlated Electrons · Physics 2025-10-21 W. Makhlouf , B. Senjean , E. Fromager

Coupled cluster calculations are traditionally performed over Hartree-Fock reference orbitals (HF-CC methodology). However, it has been repeatedly argued in the literature that the use of a Kohn-Sham reference (KS-CC methodology) might…

Chemical Physics · Physics 2025-03-10 Zsolt Benedek , Paula Tímár , Tibor Szilvási , Gergely Barcza

The recently developed localized orbital scaling correction (LOSC) method shows the ability to systematically and size-consistently reduce the delocalization error existing in conventional density functional approximations (DFAs). Applying…

Chemical Physics · Physics 2020-10-19 Yuncai Mei , Zehua Chen , Weitao Yang

A novel concept of multiconfigurational self-consistent field method, the generalized occupation-restricted-multiple-active-space (GORMAS) is presented. GORMAS wave functions are defined by substituting the complete active space (CAS) in…

Chemical Physics · Physics 2021-12-01 Chen Yang , Yoshihiro Watanabe , Haruyuki Nakano

The rapid discovery of new chemical compounds is essential for advancing global health and developing treatments. While generative models show promise in creating novel molecules, challenges remain in ensuring the real-world applicability…

Biomolecules · Quantitative Biology 2025-09-29 Onur Boyar , Hiroyuki Hanada , Ichiro Takeuchi

Electronic structure calculations, such as in the Hartree-Fock or Kohn-Sham density functional approach, require an initial guess for the molecular orbitals. The quality of the initial guess has a significant impact on the speed of…

Chemical Physics · Physics 2019-03-13 Susi Lehtola

In the present letter, it is demonstrated how full configuration interaction (FCI) results in extended basis sets may be obtained to within sub-kJ/mol accuracy by decomposing the energy in terms of many-body expansions in the virtual…

Chemical Physics · Physics 2017-09-15 Janus J. Eriksen , Filippo Lipparini , Jürgen Gauss

In this work, we investigate the possibility of improving multireference-driven coupled cluster (CC) approaches with an algorithm that iteratively combines complete active space (CAS) calculations with tailored CC and externally corrected…

Chemical Physics · Physics 2025-03-06 Robin Feldmann , Max Mörchen , Jakub Lang , Michał Lesiuk , Markus Reiher

Functionals that explicitly depend on occupied, unoccupied, or fractionally-occupied orbitals are rigorously formalized using Clifford algebras, and a variational principle is established that facilitates orbital (and occupation)…

Quantum Physics · Physics 2024-04-26 Neil Qiang Su

Localized orbitals are important for modeling and interpreting complicated electronic structures of atoms and molecules in a chemically meaningful way. Here, we present the parameter-free procedure for transforming delocalized molecular…

Chemical Physics · Physics 2018-04-12 Tymofii Yu. Nikolaienko , Leonid A. Bulavin