Ultrafast ab Initio Quantum Chemistry Using Matrix Product States

We propose a method to calculate the spectral functions of many-body systems by Chebyshev expansion in the framework of matrix product states coupled with canonical orthogonalization (coCheMPS). The canonical orthogonalization can improve the accuracy and efficiency significantly because the orthogonalized Chebyshev vectors can provide an ideal basis for constructing the effective Hamiltonian in which the exact recurrence relation can be retained. In addition, not only the spectral function but also the excited states and eigen energies can be directly calculated, which is usually impossible for other MPS-based methods such as time-dependent formalism or correction vector. The remarkable accuracy and efficiency of coCheMPS over other methods are demonstrated by calculating the spectral functions of spin chain and ab initio hydrogen chain. For the first time we demonstrate that Chebyshev MPS can be used to deal with ab initio electronic Hamiltonian effectively. We emphasize the strength of coCheMPS to calculate the low excited states of systems with sparse discrete spectrum. We also caution the application for electron-phonon systems with dense density of states.

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Thermodynamic Data of Iodine Reactions Calculated by Quantum Chemistry. Training Set of Molecules

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20081340 ◽

2008 ◽

Vol 73 (10) ◽

pp. 1340-1356 ◽

Cited By ~ 14

Author(s):

Katarína Mečiarová ◽

Laurent Cantrel ◽

Ivan Černušák

Keyword(s):

Quantum Chemistry ◽

Ab Initio ◽

Thermodynamic Data ◽

Theoretical Calculations ◽

Reactor Core ◽

Fission Products ◽

Vapour Phase ◽

Reactor Accident ◽

Training Set ◽

Coolant System

This paper focuses on the reactivity of iodine which is the most critical radioactive contaminant with potential short-term radiological consequences to the environment. The radiological risk assessments of 131I volatile fission products rely on studies of the vapour-phase chemical reactions proceeding in the reactor coolant system (RCS), whose function is transferring the energy from the reactor core to a secondary pressurised water line via the steam generator. Iodine is a fission product of major importance in any reactor accident because numerous volatile iodine species exist under reactor containment conditions. In this work, the comparison of the thermodynamic data obtained from the experimental measurements and theoretical calculations (approaching "chemical accuracy") is presented. Ab initio quantum chemistry methods, combined with a standard statistical-thermodynamical treatment and followed by inclusion of small energetic corrections (approximating full configuration interaction and spin-orbit effects) are used to calculate the spectroscopic and thermodynamic properties of molecules containing atoms H, O and I. The set of molecules and reactions serves as a benchmark for future studies. The results for this training set are compared with reference values coming from an established thermodynamic database. The computed results are promising enough to go on performing ab initio calculations in order to predict thermo-kinetic parameters of other reactions involving iodine-containing species.

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Optimal sampling of dynamical large deviations via matrix product states

Physical Review E ◽

10.1103/physreve.103.062144 ◽

2021 ◽

Vol 103 (6) ◽

Author(s):

Luke Causer ◽

Mari Carmen Bañuls ◽

Juan P. Garrahan

Keyword(s):

Large Deviations ◽

Matrix Product ◽

Optimal Sampling ◽

Matrix Product States

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Vibrational branching ratios and radiative lifetimes in the laser cooling of AlBr

Physical Chemistry Chemical Physics ◽

10.1039/c6cp08181a ◽

2017 ◽

Vol 19 (7) ◽

pp. 5519-5524 ◽

Cited By ~ 1

Author(s):

Yufeng Gao ◽

Mingjie Wan

Keyword(s):

Quantum Chemistry ◽

Ab Initio ◽

Laser Cooling ◽

Branching Ratios ◽

Radiative Lifetimes

The feasibility of laser cooling of the AlBr molecule is investigated usingab initioquantum chemistry.

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iSPECTRON : A simulation interface for linear and nonlinear spectra with ab‐initio quantum chemistry software

Journal of Computational Chemistry ◽

10.1002/jcc.26485 ◽

2021 ◽

Vol 42 (9) ◽

pp. 644-659 ◽

Cited By ~ 1

Author(s):

Francesco Segatta ◽

Artur Nenov ◽

Daniel R. Nascimento ◽

Niranjan Govind ◽

Shaul Mukamel ◽

...

Keyword(s):

Quantum Chemistry ◽

Ab Initio ◽

Linear And Nonlinear

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Multimolecular complexes of the phosphodiester anion with Zn( II ) or Mg( II ) and water molecules—Preliminary validations of a polarizable potential by ab initio quantum chemistry

Journal of Computational Chemistry ◽

10.1002/jcc.26555 ◽

2021 ◽

Author(s):

Nohad Gresh ◽

David Perahia

Keyword(s):

Quantum Chemistry ◽

Ab Initio ◽

Water Molecules

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Using Matrix-Product States for Open Quantum Many-Body Systems: Efficient Algorithms for Markovian and Non-Markovian Time-Evolution

Entropy ◽

10.3390/e22090984 ◽

2020 ◽

Vol 22 (9) ◽

pp. 984

Author(s):

Regina Finsterhölzl ◽

Manuel Katzer ◽

Andreas Knorr ◽

Alexander Carmele

Keyword(s):

Time Evolution ◽

Nearest Neighbor ◽

Matrix Product ◽

Body System ◽

Many Body ◽

Initial State ◽

Matrix Product States ◽

Open Quantum ◽

Many Body Systems ◽

The Many

This paper presents an efficient algorithm for the time evolution of open quantum many-body systems using matrix-product states (MPS) proposing a convenient structure of the MPS-architecture, which exploits the initial state of system and reservoir. By doing so, numerically expensive re-ordering protocols are circumvented. It is applicable to systems with a Markovian type of interaction, where only the present state of the reservoir needs to be taken into account. Its adaption to a non-Markovian type of interaction between the many-body system and the reservoir is demonstrated, where the information backflow from the reservoir needs to be included in the computation. Also, the derivation of the basis in the quantum stochastic Schrödinger picture is shown. As a paradigmatic model, the Heisenberg spin chain with nearest-neighbor interaction is used. It is demonstrated that the algorithm allows for the access of large systems sizes. As an example for a non-Markovian type of interaction, the generation of highly unusual steady states in the many-body system with coherent feedback control is demonstrated for a chain length of N=30.

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