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We formulate and implement the core-valence separated multireference equation-of-motion driven similarity renormalization group method (CVS-IP-EOM-DSRG) for simulating X-ray photoelectron spectra (XPS) of strongly correlated molecular…

Chemical Physics · Physics 2025-09-29 Shuhang Li , Zijun Zhao , Francesco A. Evangelista

The first nonperturbative version of the multireference driven similarity renormalization group (MR-DSRG) theory [C. Li and F. A. Evangelista, J. Chem. Theory Comput. $\mathbf{11}$, 2097 (2015)] is introduced. The renormalization group…

Chemical Physics · Physics 2016-05-25 Chenyang Li , Francesco A. Evangelista

A third-order multireference perturbation theory based on the driven similarity renormalization group approach (DSRG-MRPT3) is presented. The DSRG-MRPT3 method has several appealing features: a) it is intruder free, b) it is size…

Chemical Physics · Physics 2017-04-26 Chenyang Li , Francesco A. Evangelista

The double ionization potential (DIP) equation-of-motion (EOM) coupled-cluster (CC) method with 4-hole--2-particle (4$h$-2$p$) excitations on top of the CC with singles, doubles, and triples calculation, abbreviated as…

The accurate computation of excited states remains a challenge in electronic structure theory, especially for systems with a ground state that requires a multireference treatment. In this work, we introduce a novel equation-of-motion (EOM)…

Chemical Physics · Physics 2025-05-28 Shuhang Li , Zijun Zhao , Francesco A. Evangelista

We have devised and implemented a local ab initio Density Matrix Renormalization Group (DMRG) algorithm to describe multireference nondynamic correlations in large systems. For long molecules that are extended in one of their spatial…

Strongly Correlated Electrons · Physics 2009-11-11 Johannes Hachmann , Wim Cardoen , Garnet Kin-Lic Chan

We introduce the Nuclear Electronic All-Particle Density Matrix Renormalization Group (NEAP-DMRG) method for solving the time-independent Schr\"odinger equation simultaneously for electrons and other quantum species. In contrast to already…

Chemical Physics · Physics 2020-05-29 Andrea Muolo , Alberto Baiardi , Robin Feldmann , Markus Reiher

Applications of the similarity renormalization group (SRG) approach [F. Wegner, Ann. Phys. 506, 77 (1994), S. D. G{\l}azek and K. G. Wilson, Phys. Rev. D 49, 4214 (1994)] to the formulation of useful many-body theories of electron…

Chemical Physics · Physics 2015-06-19 Francesco A. Evangelista

We report the general implementation of the relativistic equation-of-motion coupled-cluster method to calculate double ionization spectra (DI-EOMCC) of atomic and molecular systems. As a first application, this method is employed to…

Atomic Physics · Physics 2014-08-25 Himadri Pathak , Aryya Ghosh , B. K. Sahoo , B. P. Das , Nayana Vaval , Sourav Pal

We present a recently-developed renormalization group scheme, the functional renormalization group (fRG), as a many-particle method suited to account for the two-particle interactions between the electrons in complex quantum dot geometries.…

Strongly Correlated Electrons · Physics 2007-05-23 C. Karrasch

We report the implementation of 4-component spinor relativistic equation-of-motion coupledcluster method within the single- and double- excitation approximation to calculate ionization potential (EOM-CCSD) of molecules. We have applied this…

Chemical Physics · Physics 2015-02-25 Himadri Pathak , Sudip Sasmal , Malaya K. Nayak , Nayana Vaval , Sourav Pal

The double ionization potential (DIP) equation-of-motion (EOM) coupled-cluster (CC) method with a full treatment of 4-hole-2-particle (4$h$-2$p$) correlations and triply excited clusters, abbreviated as DIP-EOMCCSDT(4$h$-2$p$), and its…

Chemical Physics · Physics 2025-02-12 Karthik Gururangan , Achintya Kumar Dutta , Piotr Piecuch

In this work, we combine the many-body formulation of the internally contracted multireference coupled cluster (ic-MRCC) method with Evangelista's multireference formulation of the driven similarity renormalization group (DSRG). The DSRG…

Chemical Physics · Physics 2025-03-04 Robin Feldmann , Markus Reiher

We present two new methods for performing ab initio calculations of excited states for closed-shell systems within the in-medium similarity renormalization group (IMSRG) framework. Both are based on combining the IMSRG with simple many-body…

Nuclear Theory · Physics 2017-05-10 N. M. Parzuchowski , T. D. Morris , S. K. Bogner

We use the functional Renormalisation Group (fRG) to describe the in and out of equilibrium dynamics of stochastic processes, governed by an overdamped Langevin equation. Exploiting the connection between Langevin dynamics and…

Statistical Mechanics · Physics 2021-02-05 Ashley Wilkins , Gerasimos Rigopoulos , Enrico Masoero

We formulate the In-Medium Similarity Renormalization Group (IM-SRG) for open-shell nuclei using a multi-reference formalism based on a generalized Wick theorem introduced in quantum chemistry. The resulting multi-reference IM-SRG…

Nuclear Theory · Physics 2013-06-13 H. Hergert , S. Binder , A. Calci , J. Langhammer , R. Roth

The article deals with the extension of the relativistic double-ionization equation-of-motion coupled-cluster (DI-EOMCC) method [H. Pathak et al. Phys. Rev. A 90, 010501(R) (2014)] for the molecular systems. The Dirac-Coulomb (DC)…

Chemical Physics · Physics 2020-04-22 Himadri Pathak , Sudip Sasmal , Kaushik Talukdar , Malaya K. Nayak , Nayana Vaval , Sourav Pal

We combine the electron attachment (EA) and ionization potential (IP) equation-of-motion (EOM) coupled-cluster (CC) approaches with the CC($P$;$Q$) formalism. The resulting methodologies are used to describe the electronic states of several…

Chemical Physics · Physics 2025-09-19 Karthik Gururangan , Stephen H. Yuwono , A. Eugene DePrince , Piotr Piecuch

Over the past decade the in-medium similarity renormalization group (IMSRG) approach has proven to be a powerful and versatile ab initio many-body method for studying medium-mass nuclei. So far, the IMSRG was limited to the approximation in…

Nuclear Theory · Physics 2021-04-27 M. Heinz , A. Tichai , J. Hoppe , K. Hebeler , A. Schwenk

We report a spin-free formulation of the multireference (MR) driven similarity renormalization group (DSRG) by employing the ensemble normal ordering of Mukherjee and Kutzelnigg [W. Kutzelnigg and D. Mukherjee, J. Chem. Phys. 107, 432…

Chemical Physics · Physics 2021-10-04 Chenyang Li , Francesco A. Evangelista
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