Article
Chemistry, Physical
Moneesha Ravi, Ajith Perera, Young Choon Park, Rodney J. Bartlett
Summary: In this paper, a study of excited states using tailored coupled cluster singles and doubles is reported. The pCCD wavefunction is used as a kernel in the more complete CCSD calculations to obtain improved results, especially in the singlet-triplet splitting of diradical molecules.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Daniil A. Fedotov, Sonia Coriani, Christof Haettig
Summary: The study presents an implementation of a complex solver for computing the complex response functions of damped response theory. The solver uses a partitioned formulation to avoid storing double excitation amplitudes, making it widely applicable in the context of the resolution-of-identity (RI) coupled cluster singles and approximate doubles (CC2) method.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Eirik F. F. Kjonstad, Henrik Koch
Summary: We present an efficient implementation of analytical non-adiabatic derivative coupling elements for the coupled cluster singles and doubles model. The derivative coupling elements are evaluated using a biorthonormal formulation, in which the nuclear derivative acts on the right electronic state, which is biorthonormal with respect to the set of left states. This implementation differs from previous methods based on normalized states and a gradient formula for the derivative coupling. As an illustration, the minimum energy conical intersection between the np* and pp* states in the nucleobase thymine is determined.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Quantum Science & Technology
Rongxin Xia, Sabre Kais
Summary: VQE is considered a major potential application of near term quantum computing for electronic structure calculations. The UCCSD VQE ansatz has achieved high accuracy, but requires extra terms for parity when using the Jordan-Wigner transformation. The proposed VQE ansatz based on particle preserving exchange gate has a gate complexity up-bounded to O(n(4)) for all-to-all connectivity, and provides very accurate results for simple molecular systems.
QUANTUM SCIENCE AND TECHNOLOGY
(2021)
Article
Chemistry, Physical
Rahul Chakraborty, Katharina Boguslawski, Pawel Tecmer
Summary: This research proposes a novel wave function theory in a density functional theory (WTF-in-DFT) embedding scheme based on pair-coupled cluster doubles (pCCD)-type methods. The method can reliably describe strongly-correlated systems with mean-field-like computational cost and has been tested for the excitation energies of various molecular structures. The results show that it is an effective computational method for excited states in large molecular systems.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Artur Nowak, Katharina Boguslawski
Summary: Numerous numerical studies have shown that geminal-based methods have great potential to model strongly correlated systems with low computational costs. Several strategies have been introduced to capture the missing dynamical correlation effects, including a posteriori corrections and inter-geminal correlations. This article examines the accuracy of the pair coupled cluster doubles (pCCD) method extended by configuration interaction (CI) theory, and finds that the proposed CI methods considerably improve spectroscopic constants compared to conventional CCSD approach.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Zhigang Ni, Yang Guo, Frank Neese, Wei Li, Shuhua Li
Summary: The paper introduces a cluster-in-molecule (CIM) local correlation approach with an accurate distant pair correlation energy correction, which is crucial for predicting absolute correlation energies and relative energies in large systems. Benchmark calculations demonstrate that the improved CIM approach can recover over 99.94% of the correlation energy calculated by the parent method, providing accurate binding energies for weakly bound complexes of varying sizes.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Chemistry, Physical
Fabijan Pavosevic, Zhen Tao, Sharon Hammes-Schiffer
Summary: The nuclear quantum effects are incorporated into quantum chemistry calculations using the nuclear-electronic orbital (NEO) approach, which includes both traditional and t1-transformed NEO coupled cluster methods with a density fitting scheme. The NEO-DF-CCSD method, with enhanced computational efficiency, accurately predicts proton affinities and successfully predicts the energy ordering of protonated water tetramers with multiple quantum protons. This work showcases the capabilities of the NEO-DF-CCSD method and lays the foundation for future developments and applications.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Karol Kowalski
Summary: In this Communication, numerical evidence is provided to suggest alternative calculation methods for the standard single-reference coupled-cluster (CC) energies. It is demonstrated that the CC energies can be reconstructed by diagonalizing the effective Hamiltonians that describe correlated sub-systems. In an extreme case, it is shown that the CC energy can be reproduced by diagonalizing the effective Hamiltonian of a sub-system composed of a single electron. These properties of the CC formalism can be utilized to design protocols for defining effective interactions in sub-systems and introduce a new type of self-consistency for approximate CC approaches.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Hans-Joachim Werner, Andreas Hansen
Summary: An overview of the approximations in explicitly correlated local coupled cluster methods PNO-LCCSD(T)-F12 and DLPNO-CCSD(T)(F12) is provided. The selection options for projected atomic orbitals (PAOs), pair natural orbitals (PNOs), and triples natural orbitals (TNOs) in both Molpro and ORCA programs are described and compared. The PNO-LCCSD(T)-F12 method is applied to compute new reference energies for benchmark sets, showing promising accuracy and computational efficiency.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Chemistry, Physical
Juan E. Arias-Martinez, Leonardo A. Cunha, Katherine J. Oosterbaan, Joonho Lee, Martin Head-Gordon
Summary: This study investigates the use of orbital-optimized references in conjunction with CCSD theory for studying core excitations and ionizations of small organic molecules. Three schemes are employed to address convergence difficulties and spin contamination. The Delta CCSD schemes significantly reduce statistical errors compared to the FC-CVS EOM-CCSD approach.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Pierre-Francois Loos, Denis Jacquemin
Summary: In this study, coupled-cluster methods were used to investigate the vertical excitation energies of 10 bicyclic molecules, providing reference values for 91 excited states and comparing various wave function methods. The results show that the accuracy of some methods remains largely unaffected by system size, while others may deteriorate significantly or become more accurate as the systems grow.
JOURNAL OF PHYSICAL CHEMISTRY A
(2021)
Article
Chemistry, Physical
Artur Nowak, Ors Legeza, Katharina Boguslawski
Summary: Wave functions based on electron-pair states provide reliable models for describing quantum many-body problems with strongly correlated electrons, especially when broken-pair states are corrected appropriately. The study analyzes the performance of electron-pair methods in predicting orbital-based correlation spectra, focusing on the pCCD-LCC ansatz. It is found that pCCD-LCC accurately reproduces orbital-pair correlation patterns in weak correlation limits and for molecules close to their equilibrium structure.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Harper R. Grimsley, Nicholas J. Mayhall
Summary: The recent quantum information boom has revitalized interest in the unitary coupled cluster (UCC) theory. This paper explores the classical approach of truncating the Taylor series expansion of UCCSD energy at the second order, instead of using perturbative expansion. The approach utilizes derivatives of order three or greater to partially recover the variational lower bound of true UCCSD, simplifying the model by restricting these derivatives. Testing on several potential energy surfaces and reaction energies reveals that this diagonal approximation effectively reduces sensitivity near singularities in strongly correlated regimes without significantly diminishing the accuracy of weakly correlated systems.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
Article
Chemistry, Physical
Yangqiu Liu, Hexiang Qi, Ming Lei
Summary: The improved elastic image pair (EIP) method is a reliable approach to approximate transition states between two local minima. By modifying the moving procedure and convergence strategy of the image pair, combined with rational function optimization, exact transition states can be achieved. Testing on a set of 45 different reactions demonstrates the reliability and efficiency of this method in finding transition states.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Chemistry, Physical
Zhigang Ni, Yang Guo, Frank Neese, Wei Li, Shuhua Li
Summary: The paper introduces a cluster-in-molecule (CIM) local correlation approach with an accurate distant pair correlation energy correction, which is crucial for predicting absolute correlation energies and relative energies in large systems. Benchmark calculations demonstrate that the improved CIM approach can recover over 99.94% of the correlation energy calculated by the parent method, providing accurate binding energies for weakly bound complexes of varying sizes.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Chemistry, Inorganic & Nuclear
Maxime Tarrago, Christina Roemelt, Joscha Nehrkorn, Alexander Schnegg, Frank Neese, Eckhard Bill, Shengfa Ye
Summary: Iron porphyrins are highly efficient catalysts for electrochemical CO2-to-CO conversion. The electronic structure of the prototypical square-planar [Fe-II(TPP)] complex has been investigated comprehensively, revealing a unique multiconfigurational nature with accidental near-triple degeneracy.
INORGANIC CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Vijay Gopal Chilkuri, Frank Neese
Summary: The full configuration interaction method is limited to small molecules, while selected CI is used to approximate FCI energies for larger molecules. Challenges in constructing an efficient algorithm include the lack of structure in the Hamiltonian, large number of electrons, and orbital spaces. Through tree-based methods and focus on total spin squared operator and multi-particle bases, the CI problem is addressed. The paper discusses logic behind algorithm design, advantages of different particle bases, and demonstrates how tree simplifies key algorithms for efficient CI program design.
JOURNAL OF COMPUTATIONAL CHEMISTRY
(2021)
Article
Chemistry, Physical
Bikramjit Sharma, Van Anh Tran, Tim Pongratz, Laura Galazzo, Irina Zhurko, Enrica Bordignon, Stefan M. Kast, Frank Neese, Dominik Marx
Summary: This study aimed to calculate the isotropic hyperfine coupling constant of a pH-sensitive spin probe in a solution using advanced computational techniques and compare it with experimental measurements. The investigation focused on advancing the calculation of EPR parameters in aqueous solutions based on rigorous statistical mechanics and correlated electronic structure techniques. The results showed that computational strategies incorporating explicit water or RISM solvation with DLPNO-CCSD calculations provided accurate predictions for the spin probe's behavior in aqueous solutions.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Chemistry, Physical
Lucas Lang, Enrico Ravera, Giacomo Parigi, Claudio Luchinat, Frank Neese
Summary: This study elaborated on the derivation of the correct long-distance limit of pseudo-contact nuclear magnetic resonance chemical shifts from rigorous first-principles quantum mechanics, confirming the classical Kurland-McGarvey theory. The study also discussed the application of the point-dipole approximation (PDA) in approximate density functional theory and Hartree-Fock theories, and demonstrated how it is possible to overcome the previous assumption of a crude effective nuclear charge approximation by using the fully relativistic Dirac equation.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Rami Shafei, Dimitrios Maganas, Philipp Jean Strobel, Peter J. Schmidt, Wolfgang Schnick, Frank Neese
Summary: In this study, a computational protocol is developed to predict the absorption and emission spectral shapes of Eu2+-doped phosphors. The energy distribution and band shape of the emission spectrum are found to be related to the nature of the 4f-5d transitions in the absorption process. Simple descriptors are identified that show a strong correlation with the energy position and bandwidth of the experimental emission bands.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
Frank Neese
Summary: The latest version 5.0 of the ORCA quantum chemistry program suite represents a significant improvement in performance, numerical robustness, functionality, and user friendliness.
WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE
(2022)
Article
Chemistry, Physical
Nicolas O. Foglia, Dimitrios Maganas, Frank Neese
Summary: In this work, a time-dependent density functional theory (TD-DFT) scheme for computing optical spectroscopic properties in the framework of linearly and circularly polarized light is presented. The scheme can calculate absorption, circular dichroism, and magnetic circular dichroism spectra, and takes into account relativistic effects and random orientations of molecules.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Robert Izsak, Christoph Riplinger, Nick S. Blunt, Bernardo de Souza, Nicole Holzmann, Ophelia Crawford, Joan Camps, Frank Neese, Patrick Schopf
Summary: Quantum computers are expected to be useful in simulating strongly correlated chemical systems, but careful selection of orbital spaces is crucial. This study presents a scheme for automatically selecting an active space and combines quantum phase estimation and variational quantum eigensolver algorithms to accurately describe the environment. The protocol outlined here can be applied to chemical systems of any size, including those beyond the capabilities of classical computation.
JOURNAL OF COMPUTATIONAL CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Frank Neese
Summary: This paper describes the SHARK integral generation and digestion engine, which is based on the McMurchie/Davidson approach and utilizes an efficient BLAS algorithm. SHARK can handle various types of basis function integrals and features programming constructs that simplify workflows and avoid code duplication.
JOURNAL OF COMPUTATIONAL CHEMISTRY
(2023)
Meeting Abstract
Biochemistry & Molecular Biology
Sinjini Bhattacharjee, Frank Neese, Dimitrios A. Pantazis
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
(2022)
Article
Chemistry, Multidisciplinary
Ingolf Harden, Frank Neese, Giovanni Bistoni
Summary: This study investigates the aggregation process of chiral organocatalysts derived from phosphoric acids using high-level quantum mechanical calculations. The results show that the formation of catalyst dimers is possible and the aggregation process can significantly affect the stereo-controlling factors, reaction kinetics, and selectivity of the transformations.
Article
Chemistry, Multidisciplinary
Ingolf Harden, Frank Neese, Giovanni Bistoni
Summary: The formation of Bronsted acid aggregates in asymmetric organocatalytic reactions has a significant impact on the stereo-controlling factors of the transformations. This study uses high-level quantum mechanical calculations to investigate the influence of catalyst structure and reaction conditions on the spontaneity of the aggregation process, shedding light on its importance.
Article
Chemistry, Physical
M. Atanasov, N. Spiller, F. Neese
Summary: This study uses first principles calculations to simulate magnetic and spectroscopic data, providing an explanation for the stability of a mixed valence binuclear transition metal complex. The study also proposes a new model to interpret the magnetic behavior of the complex.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Andrew M. Teale, Trygve Helgaker, Andreas Savin, Carlo Adamo, Balint Aradi, Alexei Arbuznikov, Paul W. Ayers, Evert Jan Baerends, Vincenzo Barone, Patrizia Calaminici, Eric Cances, Emily A. Carter, Pratim Kumar Chattaraj, Henry Chermette, Ilaria Ciofini, T. Daniel Crawford, Frank De Proft, John F. Dobson, Claudia Draxl, Thomas Frauenheim, Emmanuel Fromager, Patricio Fuentealba, Laura Gagliardi, Giulia Galli, Jiali Gao, Paul Geerlings, Nikitas Gidopoulos, Peter M. W. Gill, Paola Gori-Giorgi, Andreas Gorling, Tim Gould, Stefan Grimme, Oleg Gritsenko, Hans Jorgen Aagaard Jensen, Erin R. Johnson, Robert O. Jones, Martin Kaupp, Andreas M. Koster, Leeor Kronik, Anna Krylov, Simen Kvaal, Andre Laestadius, Mel Levy, Mathieu Lewin, Shubin Liu, Pierre-Francois Loos, Neepa T. Maitra, Frank Neese, John P. Perdew, Katarzyna Pernal, Pascal Pernot, Piotr Piecuch, Elisa Rebolini, Lucia Reining, Pina Romaniello, Adrienn Ruzsinszky, Dennis R. Salahub, Matthias Scheffler, Peter Schwerdtfeger, Viktor N. Staroverov, Jianwei Sun, Erik Tellgren, David J. Tozer, Samuel B. Trickey, Carsten A. Ullrich, Alberto Vela, Giovanni Vignale, Tomasz A. Wesolowski, Xin Xu, Weitao Yang
Summary: This paper provides an informal review and discussion on the history, present status, and future of density-functional theory (DFT) by 70 workers in the field. The format of a roundtable discussion allowed participants to express their views through 302 individual contributions to a preset list of 26 questions. Supported by a bibliography of 777 entries, the paper offers a comprehensive snapshot of DFT in 2022.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)