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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

Most nonrelativistic electron correlation methods can be adapted to account for relativistic effects, as long as the relativistic molecular spinor integrals are available, from either a four-, two-, or one-component mean-field calculation.…

Strongly Correlated Electrons · Physics 2024-07-17 Zijun Zhao , Francesco A. Evangelista

We present an efficient and exact Monte Carlo algorithm to simulate reversible aggregation of particles with dedicated binding sites. This method introduces a novel data structure of dynamic bond tree to record clusters and sequences of…

Quantitative Methods · Quantitative Biology 2011-09-27 Qiang Chang , Jin Yang

We present a spin-free, size-extensive, and size-consistent coupled cluster method based on a generalised normal ordered exponential ansatz. This approach is a natural generalisation of single-reference coupled cluster theory for arbitrary…

Chemical Physics · Physics 2025-07-21 Nicholas Lee , David P. Tew

We present a near-linear scaling formulation of the explicitly-correlated coupled-cluster singles and doubles with perturbative triples method (CCSD(T)$_{\overline{\text{F12}}}$) for high-spin states of open-shell species. The approach is…

Chemical Physics · Physics 2024-07-30 Ashutosh Kumar , Frank Neese , Edward F. Valeev

We present efficient implementations of the multilevel CC2 (MLCC2) and multilevel CCSD (MLCCSD) models. As the system size increases, MLCC2 and MLCCSD exhibit the scaling of the lower level coupled cluster model. In order to treat large…

Chemical Physics · Physics 2020-11-25 Sarai D. Folkestad , Eirik F. Kjønstad , Linda Goletto , Henrik Koch

A second-order many-body perturbation correction to the relativistic Dirac-Hartree-Fock energy is evaluated stochastically by integrating 13-dimensional products of four-component spinors and Coulomb potentials. The integration in the real…

Quantum Physics · Physics 2022-06-16 J. César Cruz , Jorge Garza , Takeshi Yanai , So Hirata

The computationally expensive evaluation and storage of high-rank reduced density matrices (RDMs) has been the bottleneck in the calculation of dynamic correlation for multireference wave functions in large active spaces. We present a…

Chemical Physics · Physics 2020-01-08 Ankit Mahajan , Nick S. Blunt , Iliya Sabzevari , Sandeep Sharma

The iterative qubit coupled cluster (iQCC) method is a systematic variational approach to solve the electronic structure problem on universal quantum computers. It is able to use arbitrarily shallow quantum circuits at expense of iterative…

Quantum Physics · Physics 2020-09-30 Ilya G. Ryabinkin , Artur F. Izmaylov , Scott N. Genin

In order to explore the effects of high levels of electron correlation on the real-time coupled cluster formalism and algorithmic behavior, we introduce a time-dependent implementation of the CC3 singles, doubles and approximate triples…

Chemical Physics · Physics 2025-01-23 Zhe Wang , Håkon Emil Kristiansen , Thomas Bondo Pedersen , T. Daniel Crawford

An improved version of a recently developed stochastic cluster dynamics (SCD) method {[}Marian, J. and Bulatov, V. V., {\it J. Nucl. Mater.} \textbf{415} (2014) 84-95{]} is introduced as an alternative to rate theory (RT) methods for…

Data Structures and Algorithms · Computer Science 2016-05-04 Tuan L. Hoang , Jaime Marian , Vasily V. Bulatov , Peter Hosemann

We introduce a unitary coupled-cluster (UCC) ansatz termed $k$-UpCCGSD that is based on a family of sparse generalized doubles (D) operators which provides an affordable and systematically improvable unitary coupled-cluster wavefunction…

Quantum Physics · Physics 2019-01-07 Joonho Lee , William J. Huggins , Martin Head-Gordon , K. Birgitta Whaley

The simultaneous treatment of static and dynamical correlations in strongly-correlated electron systems is a critical challenge. In particular, finding a universal scheme for identifying a single-particle orbital basis that minimizes the…

Quantum Physics · Physics 2024-08-07 Ke Liao , Lexin Ding , Christian Schilling

Computer simulation with Monte Carlo is an important tool to investigate the function and equilibrium properties of many systems with biological and soft matter materials solvable in solvents. The appropriate treatment of long-range…

Computational Physics · Physics 2015-06-15 Zecheng Gan , Zhenli Xu

The Gyrokinetic Toroidal Code at Princeton (GTC-P) is a highly scalable and portable particle-in-cell (PIC) code. It solves the 5D Vlasov-Poisson equation featuring efficient utilization of modern parallel computer architectures at the…

Distributed, Parallel, and Cluster Computing · Computer Science 2015-10-20 Bei Wang , Stephane Ethier , William Tang , Khaled Ibrahim , Kamesh Madduri , Samuel Williams , Leonid Oliker

Full Configuration Interaction Quantum Monte Carlo (FCIQMC) has been effectively applied to very large configuration interaction (CI) problems, and was recently adapted for use as an active space solver and combined with orbital…

Chemical Physics · Physics 2020-02-19 Robert J. Anderson , Toru Shiozaki , George H. Booth

The Trotterized Unitary Coupled Cluster Single and Double (UCCSD) ansatz has recently attracted interest due to its use in Variation Quantum Eigensolver (VQE) molecular simulations on quantum computers. However, when the size of molecules…

Chemical Physics · Physics 2023-05-29 Mohammad Haidar , Marko J. Rančić , Yvon Maday , Jean-Philip Piquemal

Density functionals at the level of the Generalized Gradient Approximation (GGA) and a plane-wave basis set are widely used today to perform ab initio molecular dynamics (AIMD) simulations. Going up in the ladder of accuracy of density…

Computational Physics · Physics 2021-10-18 Sagarmoy Mandal , Ritama Kar , Tobias Kloeffel , Bernd Meyer , Nisanth N. Nair

Ion cyclotron resonance energization (ICRE) such as ion cyclotron resonance heating (ICRH) is widely applied to magnetic confinement fusion and high-power electric propulsion. Since ICRE involves cyclotron resonance processes, a kinetic…

Plasma Physics · Physics 2024-01-11 Mingyang Wu , Andong Xu , Chijie Xiao

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