Best‐Practice DFT Protocols for Basic Molecular Computational Chemistry**

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(42)

Published: Sept. 14, 2022

Nowadays, many chemical investigations are supported by routine calculations of molecular structures, reaction energies, barrier heights, and spectroscopic properties. The lion's share these quantum-chemical applies density functional theory (DFT) evaluated in atomic-orbital basis sets. This work provides best-practice guidance on the numerous methodological technical aspects DFT three parts: Firstly, we set stage introduce a step-by-step decision tree to choose computational protocol that models experiment as closely possible. Secondly, present recommendation matrix guide choice depending task at hand. A particular focus is achieving an optimal balance between accuracy, robustness, efficiency through multi-level approaches. Finally, discuss selected representative examples illustrate recommended protocols effect choices.

Language: Английский

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CRYSTAL23: A Program for Computational Solid State Physics and Chemistry

Journal of Chemical Theory and Computation, Journal Year: 2022, Volume and Issue: 19(20), P. 6891 - 6932

Published: Dec. 11, 2022

The Crystal program for quantum-mechanical simulations of materials has been bridging the realm molecular quantum chemistry to solid state physics many years, since its first public version released back in 1988. This peculiarity stems from use atom-centered basis functions within a linear combination atomic orbitals (LCAO) approach and corresponding efficiency evaluation exact Fock exchange series. In particular, this led implementation rich variety hybrid density functional approximations 1998. Nowadays, it is acknowledged by broad community chemists physicists that inclusion fraction exchange-correlation potential theory key better description properties (electronic, magnetic, mechanical, spintronic, lattice-dynamical, etc.). Here, main developments made last five years (i.e., previous release, Crystal17) are presented some their most noteworthy applications reviewed.

Language: Английский

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Best‐Practice DFT Protocols for Basic Molecular Computational Chemistry**

Angewandte Chemie, Journal Year: 2022, Volume and Issue: 134(42)

Published: Sept. 14, 2022

Abstract Nowadays, many chemical investigations are supported by routine calculations of molecular structures, reaction energies, barrier heights, and spectroscopic properties. The lion's share these quantum‐chemical applies density functional theory (DFT) evaluated in atomic‐orbital basis sets. This work provides best‐practice guidance on the numerous methodological technical aspects DFT three parts: Firstly, we set stage introduce a step‐by‐step decision tree to choose computational protocol that models experiment as closely possible. Secondly, present recommendation matrix guide choice depending task at hand. A particular focus is achieving an optimal balance between accuracy, robustness, efficiency through multi‐level approaches. Finally, discuss selected representative examples illustrate recommended protocols effect choices.

Language: Английский

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A local hybrid exchange functional approximation from first principles

The Journal of Chemical Physics, Journal Year: 2022, Volume and Issue: 157(3)

Published: June 28, 2022

Local hybrid functionals are a more flexible class of density functional approximations, allowing for position-dependent admixture exact exchange. This additional flexibility, however, comes with involved mathematical form and complicated design. A common denominator previously constructed local is the usage thermochemical benchmark data to construct these functionals. Herein, we design without relying on data. Instead, it in ab initio manner, following principles modern meta-generalized gradient approximations considering theoretical constraints. To achieve this, make use matrix expansion mixing function based an approximate correlation length. The accuracy developed approximation assessed thermochemistry, excitation energies, polarizabilities, magnetizabilities, nuclear magnetic resonance (NMR) spin-spin coupling constants, NMR shieldings, shifts, as well EPR g-tensors hyperfine constants. Here, new exchange shows robust performance especially suited atomization barrier heights, properties, whereas loses some ground shifts. Therefore, designed major step forward that have been from first principles.

Language: Английский

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Impact of the current density on paramagnetic NMR properties

The Journal of Chemical Physics, Journal Year: 2022, Volume and Issue: 157(3)

Published: June 27, 2022

Meta-generalized gradient approximations (meta-GGAs) and local hybrid functionals generally depend on the kinetic energy density τ. For magnetic properties, this necessitates generalizations to ensure gauge invariance. In most implementations, τ is generalized by incorporating external field. However, introduces artifacts in response of matrix does not satisfy iso-orbital constraint. Here, we extend previous approaches based current paramagnetic nuclear resonance (NMR) shieldings electron (EPR) g-tensors. The impact assessed for main-group compounds transition-metal complexes considering 25 functional approximations. It shown that leads substantial improvements-especially popular Minnesota strongly constrained appropriately normed (SCAN) families. Thus, recommend use NMR EPR calculations with meta-GGAs.

Language: Английский

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Paramagnetic Nuclear Magnetic Resonance Shifts for Triplet Systems and Beyond with Modern Relativistic Density Functional Methods

The Journal of Physical Chemistry A, Journal Year: 2024, Volume and Issue: 128(3), P. 670 - 686

Published: Jan. 9, 2024

An efficient framework for the calculation of paramagnetic NMR (pNMR) shifts within exact two-component (X2C) theory and (current-dependent) density functional (DFT) up to class local hybrid functionals (LHFs) is presented. Generally, pNMR systems with more than one unpaired electron depend on orbital shielding contribution a temperature-dependent term. The latter includes zero-field splitting (ZFS), hyperfine coupling (HFC), g-tensor. For consistency, we calculate these three tensors at same level theory, i.e., using scalar-relativistic X2C augmented spin–orbit perturbation theory. Results chemical transition-metal complexes reveal that this X2C–DFT can yield good results both individual tensor contributions metallocenes related systems, especially if HFC constant large. small constants, relative error often large, sometimes sign may be off. 4d 5d complicated structures demonstrate limitations fully DFT-based approach. Additionally, Co-based complex very large ZFS pronounced multireference character not well described. Here, DFT-multireference necessary accurate results. Our show sufficient describe relativistic effects computationally cheaper Thus, it allows use basis sets converged HFCs. Overall, current-dependent meta-generalized gradient approximations LHFs some potential; however, currently available leave lot desired, predictive power limited.

Language: Английский

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β-Diketonate Coordination: Vibrational Properties, Electronic Structure, Molecular Topology, and Intramolecular Interactions. Beryllium(II), Copper(II), and Lead(II) as Study Cases

The Journal of Physical Chemistry A, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 17, 2025

Nine metal complexes formed by three symmetric β-diketonates (viz., acetylacetonate (acac), 1,1,1,3,3,3-hexafluoro-acetylacetonate (hfac), and 2,2,6,6-tetramethylheptane-3,5-dionate (tmhd)) ions (with different coordination geometries, viz., BeII - tetrahedral, CuII square planar, PbII "swing" pyramidal) were investigated. The study combines structural analyses, vibrational spectroscopic techniques, quantum chemical calculations with the aim of bridging crystal structure, electronic molecular topology, far-infrared (FIR) characteristics. effect intramolecular interactions on structural, electronic, features is center this study. structure Be(tmhd)2 also reported discussed for first time. A complete review experimental IR spectra offered; discrepancies in assignments some peaks are revealed among published works. Anharmonic effects considered acac complexes; however, they negligible FIR modes. systematic comparison between computed experimentally measured data allowed us to design an inexpensive, yet efficient computational protocol investigate large polynuclear complexes.

Language: Английский

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Current density functional framework for spin–orbit coupling

The Journal of Chemical Physics, Journal Year: 2022, Volume and Issue: 157(20)

Published: Nov. 7, 2022

Relativistic two-component density functional calculations are carried out in a non-collinear formalism to describe spin-orbit interactions, where the exchange-correlation is constructed as generalization of non-relativistic approximation. Contrary theory (DFT), coupling, however, leads non-vanishing paramagnetic current density. Density functionals depending on kinetic energy density, such meta-generalized gradient approximations, should therefore be framework DFT (CDFT). The latter has previously exclusively been used regime strong magnetic fields. Herein, we present consistent CDFT approach for relativistic DFT, including coupling. Furthermore, assess importance terms ground-state energies, excitation nuclear resonance shielding, and spin-spin coupling constants, well hyperfine Δg-shifts, quadrupole interaction tensor electron (EPR) spectroscopy. most notable changes found EPR properties. impact current-dependent rises with number unpaired electrons, consequently, properties more sensitive toward CDFT. Considerable observed strongly constrained appropriately normed functionals, B97M family TASK. less important when exact exchange incorporated. At same time, kernel ensures stability response all cases. We, therefore, recommend use self-consistent calculations.

Language: Английский

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Conformational Energy Benchmark for Longer n-Alkane Chains

The Journal of Physical Chemistry A, Journal Year: 2022, Volume and Issue: 126(22), P. 3521 - 3535

Published: May 26, 2022

We present the first benchmark set focusing on conformational energies of highly flexible, long n-alkane chains, termed ACONFL. Unbranched alkanes are ubiquitous building blocks in nature, so goal is to be able calculate their properties most accurately improve modeling of, e.g., complex (biological) systems. Very accurate DLPNO-CCSD(T1)/CBS reference values provided, which allow for a statistical meaningful evaluation even best available density functional methods. The performance established and modern (dispersion corrected) functionals comprehensively assessed. recently introduced r2SCAN-V shows excellent performance, similar efficient composite DFT methods like B97-3c r2SCAN-3c, provide an better cost-accuracy ratio, while almost reaching accuracy much more computationally demanding hybrid or double with large QZ AO basis sets. In addition, we investigated common wave function methods, where MP2/CBS surprisingly performs worse compared simple D4 dispersion corrected Hartree-Fock. Furthermore, investigate several semiempirical force field commonly used generation ensembles multilevel workflows scale molecular dynamics studies. Outstanding obtained by general field, GFN-FF, other applied universal yield errors. recommend ACONFL as helpful parametrization new machine learning potentials well validation newly developed

Language: Английский

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Paramagnetic NMR Shielding Tensors Based on Scalar Exact Two-Component and Spin–Orbit Perturbation Theory

The Journal of Physical Chemistry A, Journal Year: 2022, Volume and Issue: 126(30), P. 5050 - 5069

Published: July 20, 2022

The temperature-dependent Fermi-contact and pseudocontact terms are important contributions to the paramagnetic NMR shielding tensor. Herein, we augment scalar-relativistic (local) exact two-component (X2C) framework with spin-orbit perturbation theory including screened nuclear correction for EPR hyperfine coupling g tensor compute these terms. accuracy of this perturbative ansatz is assessed self-consistent four-component treatments serving as reference. This shows that interaction sufficiently described shifts; however, larger deviations found spectra principle components properties heavy elements. impact treatment further compared density functional approximation basis set. Large-scale calculations routinely possible multipole-accelerated resolution identity seminumerical exchange approximation, shown [CeTi6O3(OiPr)9(salicylate)6].

Language: Английский

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