Accurate Geometries of Large Molecules by Integration of the Pisa Composite Scheme and the Templating Synthon Approach

Lazzari, Federico; Mendolicchio, Marco; Barone, Vincenzo

doi:10.1021/acs.jpca.3c08382

Cited by 8 publications

(3 citation statements)

References 77 publications

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“…To sum up, our results can be used for benchmarking novel state-of-the-art computations, [43,44] and the results show that, for this molecular system, MP2/6-311 + + G(d,p) gives the best results both in the structure and energy.…”

Section: Initial Computational Benchmarkmentioning

confidence: 88%

Impact of the Acetyl Group on Cysteine: A Study of N‐Acetyl‐Cysteine through Rotational Spectroscopy

Mato,

Municio,

Alonso

et al. 2024

ChemPhysChem

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Herein, we report a spectroscopic study of N‐acetyl‐L‐cysteine, an important antioxidant drug, using Fourier‐transform microwave techniques and in isolated conditions. Two conformers are observed, where most stable structure adopts a cis disposition, and the second conformer has a lower abundance and adopts a trans disposition. The rotational constants and the barriers to methyl internal rotation are determined for each conformer, allowing a precise conformation identification. The results show that the cis form adopts an identical structure in the crystal, solution, and gas phases. Additionally, the structures are contrasted against those of cysteine

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Section: Initial Computational Benchmarkmentioning

confidence: 88%

Impact of the Acetyl Group on Cysteine: A Study of N‐Acetyl‐Cysteine through Rotational Spectroscopy

Mato,

Municio,

Alonso

et al. 2024

ChemPhysChem

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show abstract

“…The way toward a cheaper model was paved by the general finding that CV correlation affects mainly bond lengths and is well represented by a simple function of the principal quantum numbers ( n i ) of the involved atoms . The final BPCS model employs an additional one-parameter function of Pauling bond orders to counterbalance the slight overestimation of delocalization typical of current functionals. , Several studies have shown that the BPCS delivers equilibrium geometries closely approaching their very accurate semiexperimental (SE) counterparts at the cost of a DFT geometry optimization. ,, In the present work, all the geometry optimizations have been performed with the Gaussian package, whereas the computation of the final BPCS geometries has been implemented in the freely available Web site (). , …”

Section: Computational Detailsmentioning

confidence: 90%

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

Mendolicchio,

Barone

2024

J. Chem. Theory Comput.

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

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“…Coming to ZPEs and entropies, the VPT2 route offers a remarkable cost/performance ratio in conjunction with PCS1 harmonic frequencies and PCS0 anharmonic contributions. Thanks to the availability of very effective engines employing finite differences of analytical Hessians, these computations can be performed for quite large molecules. , Alternatively, the much faster methods based on analytical gradients in conjunction with scaled PCS1 or, even, PCS0 harmonic frequencies usually provide sufficiently accurate results.…”

Section: Discussionmentioning

confidence: 99%

Toward Accurate Quantum Chemical Methods for Molecules of Increasing Dimension: The New Family of Pisa Composite Schemes

Di Grande,

Barone

2024

J. Phys. Chem. A

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The new versions of the Pisa composite scheme introduced in the present paper are based on the careful selection of different quantum chemical models for energies, geometries, and vibrational frequencies, with the aim of maximizing the accuracy of the overall description while retaining a reasonable cost for all the steps. In particular, the computation of accurate electronic energies has been further improved introducing more reliable complete basis set extrapolations and estimation of core−valence correlation, together with improved basis sets for third-row atoms. Furthermore, the reduced-cost frozen natural orbital (FNO) model has been introduced and validated for large molecules. Accurate molecular structures can be obtained avoiding complete basis set extrapolation and evaluating core−valence correlation at the MP2 level. Unfortunately, analytical gradients are not available for the FNO version of the model. Therefore, for large molecules, an accurate reduced-cost alternative is offered by evaluation of valence contributions with a double-hybrid functional in conjunction with the same MP2 contribution for core−valence correlation or by means of a one-parameter approximation. The same doublehybrid functional and basis set are employed to evaluate zero-point energies and partition functions. After the validation of the new models for small systems, a panel of molecular bricks of life has been used to analyze their performances for problems of current fundamental or technological interest. The fully black-box implementation of the computational workflow paves the way toward the accurate yet not prohibitively expensive study of medium-to large-sized molecules also by experimentally oriented researchers.

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Accurate Geometries of Large Molecules by Integration of the Pisa Composite Scheme and the Templating Synthon Approach

Cited by 8 publications

References 77 publications

Impact of the Acetyl Group on Cysteine: A Study of N‐Acetyl‐Cysteine through Rotational Spectroscopy

Impact of the Acetyl Group on Cysteine: A Study of N‐Acetyl‐Cysteine through Rotational Spectroscopy

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

Toward Accurate Quantum Chemical Methods for Molecules of Increasing Dimension: The New Family of Pisa Composite Schemes

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