State-Specific Coupled-Cluster Methods for Excited States

Journal of Chemical Theory and Computation, Год журнала: 2024, Номер 20(10), С. 4129 - 4145

Опубликована: Май 15, 2024

We reexamine ΔCCSD, a state-specific coupled-cluster (CC) with single and double excitations (CCSD) approach that targets excited states through the utilization of non-Aufbau determinants. This methodology is particularly efficient when dealing doubly states, domain in which standard equation-of-motion CCSD (EOM-CCSD) formalism falls short. Our goal here to evaluate effectiveness ΔCCSD applied other types comparing its consistency accuracy EOM-CCSD. To this end, we report benchmark on excitation energies computed EOM-CCSD methods for set molecular excited-state encompasses not only but also doublet–doublet transitions (singlet triplet) singly closed-shell systems. In latter case, rely minimalist version multireference CC known as two-determinant method compute states. data set, consisting 276 stemming from quest database [Véril et al., WIREs Comput. Mol. Sci. 2021, 11, e1517], provides significant base draw general conclusions concerning ΔCCSD. Except found underperforms For transitions, difference between mean absolute errors (MAEs) two methodologies (of 0.10 0.07 eV) less pronounced than obtained systems (MAEs 0.15 0.08 eV). discrepancy largely attributed greater number exhibiting multiconfigurational characters, are more challenging typically small improvements by employing optimized orbitals.

Язык: Английский

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Some Recent Advances in Density-Based Reactivity Theory

The Journal of Physical Chemistry A, Год журнала: 2024, Номер 128(7), С. 1183 - 1196

Опубликована: Фев. 8, 2024

Establishing a chemical reactivity theory in density functional (DFT) language has been our intense research interest the past two decades, exemplified by determination of steric effect and stereoselectivity, evaluation electrophilicity nucleophilicity, identification strong weak interactions, formulation cooperativity, frustration, principle chirality hierarchy. In this Featured Article, we first overview four density-based frameworks DFT to appreciate understanding, including conceptual DFT, use associated quantities, information-theoretic approach, orbital-free then present few recent advances these as well new applications from studies. To that end, will introduce relationship among frameworks, determining entire spectrum interactions with Pauli energy derivatives, performing topological analyses extending excited states. Applications examine physiochemical properties external electric fields evaluate polarizability for proteins crystals are discussed. A possible directions future development followed, special emphasis on its merger machine learning.

Язык: Английский

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Accurate Structures and Rotational Constants of Steroid Hormones at DFT Cost: Androsterone, Testosterone, Estrone, β-Estradiol, and Estriol

The Journal of Physical Chemistry A, Год журнала: 2024, Номер 128(13), С. 2629 - 2642

Опубликована: Март 26, 2024

A comprehensive analysis of the structural, conformational, and spectroscopic properties in gas phase has been performed for five prototypical steroid hormones, namely, androsterone, testosterone, estrone, β-estradiol, estriol. The revDSD-PBEP86 double-hybrid functional conjunction with D3BJ empirical dispersion a suitable triple-ζ basis set provides accurate conformational energies equilibrium molecular structures, latter being further improved by proper account core–valence correlation. Average deviations within 0.1% between computed experimental ground state rotational constants are reached when adding to those values vibrational corrections obtained at cost standard harmonic frequencies thanks use new computational tool. Together intrinsic interest studied accuracy results DFT molecules containing about 50 atoms paves way toward investigations other flexible bricks life.

Язык: Английский

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Unbiased Comparison between Theoretical and Experimental Molecular Structures and Properties: Toward an Accurate Reduced-Cost Evaluation of Vibrational Contributions

Journal of Chemical Theory and Computation, Год журнала: 2024, Номер 20(7), С. 2842 - 2857

Опубликована: Апрель 1, 2024

The tremendous development of hardware and software is constantly increasing the role quantum chemical (QC) computations in assignment interpretation experimental results. However, an unbiased comparison between theory experiment requires proper account vibrational averaging effects. In particular, high-resolution spectra gas phase are now available for molecules containing up to about 50 atoms, which too large a brute-force approach with QC methods sufficient accuracy. present paper, we introduce hybrid approaches, allow accurate evaluation effects this size beyond harmonic approximation, special attention being devoted rotational constants. After validation new tools relatively small molecules, β-estradiol hormone prototypical molecular motor have been considered witness feasibility molecules.

Язык: Английский

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Overcoming the barrier of orbital-free density functional theory for molecular systems using deep learning

Nature Computational Science, Год журнала: 2024, Номер 4(3), С. 210 - 223

Опубликована: Март 11, 2024

Язык: Английский

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Toward the Next Generation of Density Functionals: Escaping the Zero-Sum Game by Using the Exact-Exchange Energy Density

Accounts of Chemical Research, Год журнала: 2024, Номер 57(13), С. 1815 - 1826

Опубликована: Июнь 21, 2024

ConspectusKohn–Sham density functional theory (KS DFT) is arguably the most widely applied electronic-structure method with tens of thousands publications each year in a wide variety fields. Its importance and usefulness can thus hardly be overstated. The central quantity that determines accuracy KS DFT calculations exchange-correlation functional. exact form unknown, or better "unknowable", therefore derivation ever more accurate yet efficiently applicable approximate functionals "holy grail" field. In this context, simultaneous minimization so-called delocalization errors static correlation greatest challenge needs to overcome as we move toward computationally efficient methods. many cases, an improvement on one these two aspects (also often termed fractional-charge fractional-spin errors, respectively) generates deterioration other one. Here report recent notable progress escaping "zero-sum-game" by constructing new based exact-exchange energy density. particular, local hybrid range-separated are discussed incorporate additional terms deal well errors. Taking hints from coordinate-space models nondynamical strong electron correlations (the B13 KP16/B13 models), position-dependent functions cover real space have been devised incorporated into local-mixing determining position-dependence admixture hybrids treatment range separation hybrids. While initial followed closely frameworks, meanwhile simpler real-space ratios semilocal densities found, providing basis for relatively simple numerically convenient functionals. Notably, correction either increase decrease locally (and interelectronic-distance space), leading even regions negative cases particularly correlations. Efficient implementations fast computer code (Turbomole) using seminumerical integration techniques make such promising tools complicated composite systems research areas, where simultaneously small crucial. First real-world application examples provided, including stretched bonds, symmetry-breaking hyperfine coupling open-shell transition-metal complexes, reduction computation nuclear shieldings magnetizabilities. newest versions (e.g., ωLH23tdE) retain excellent frontier-orbital energies correct asymptotic potential underlying ωLH22t while improving substantially strong-correlation cases. further linked performance impactful deep-neural-network "black-box" DM21, which itself may viewed hybrid.

Язык: Английский

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Overview on Building Blocks and Applications of Efficient and Robust Extended Tight Binding

The Journal of Physical Chemistry A, Год журнала: 2025, Номер unknown

Опубликована: Фев. 27, 2025

The extended tight binding (xTB) family of methods opened many new possibilities in the field computational chemistry. Within just 5 years, GFN2-xTB parametrization for all elements up to Z = 86 enabled more than a thousand applications, which were previously not feasible with other electronic structure methods. xTB provide robust and efficient way apply quantum mechanics-based approaches obtaining molecular geometries, computing free energy corrections or describing noncovalent interactions found applicability targets. A crucial contribution success is availability within simulation packages frameworks, supported by open source development its program library packages. We present comprehensive summary applications capabilities different fields Moreover, we consider main software calculations, covering their current ecosystem, novel features, usage scientific community.

Язык: Английский

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Anomalous propagators and the particle–particle channel: Bethe–Salpeter equation

The Journal of Chemical Physics, Год журнала: 2025, Номер 162(13)

Опубликована: Апрель 3, 2025

The Bethe-Salpeter equation has been extensively employed to compute the two-body electron-hole propagator and its poles which correspond neutral excitation energies of system. Through a different time-ordering, Green's function can also describe propagation two electrons or holes. corresponding are double ionization potentials electron affinities In this work, for particle-particle is derived within linear-response formalism using pairing field anomalous propagators. This framework allows us kernels self-energy approximations ($GW$, $T$-matrix, second-Born) as in usual case. performance these various gauged singlet triplet valence set 23 small molecules. description core hole states analyzed.

Язык: Английский

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Examining the Impact of Local Constraint Violations on Energy Computations in DFT

Journal of Computational Chemistry, Год журнала: 2025, Номер 46(1)

Опубликована: Янв. 2, 2025

ABSTRACT This work examines the impact of locally imposed constraints in Density Functional Theory (DFT). Using a metric referred to as extent violation index (EVI), we quantify how well exchange‐correlation functionals adhere local constraints. Applying EVIs diverse set molecules for GGA reveals constraint violations, particularly semi‐empirical functionals. We leverage explore potential connections between these violations and errors chemical properties. While no correlation is observed atomization energies, significant statistical emerges total energies. Similarly, analysis reaction energies suggests weak positive correlations specific However, definitive conclusions about error cancellation mechanisms cannot be made at this time. These observations revealed by may useful consideration when designing future generations semilocal

Язык: Английский

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What Dictates the α-Effect in Gas-Phase S_N2 Reactions? A Density Functional Theory Study

The Journal of Physical Chemistry A, Год журнала: 2025, Номер unknown

Опубликована: Фев. 5, 2025

The α-effect is an important concept in chemistry and biochemistry, namely that for a bimolecular nucleophilic substitution (SN2) reaction, the nucleophilicity of atom increased if its adjacent (α) has lone pair electrons, lowering reaction barrier height increasing rate. However, exceptions exist, even very similar structural motifs. We investigate what underlies gas-phase SN2 reactions using two total energy decomposition schemes based on density functional theory (DFT) find steric effects play role, but there exists strong linear correlation between electrostatic contribution, suggesting it interaction stabilizes transition state leads to reactions. This multifaceted explanation resolves long-standing uncertainty about α-effect. show increases with branching central carbon atom.

Язык: Английский

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