A Hylleraas functional based perturbative technique to relax the extremely localized molecular orbital wavefunction

Genoni, Alessandro; Merz, Kenneth M.; Sironi, Maurizio

doi:10.1063/1.2961015

Cited by 16 publications

(17 citation statements)

References 56 publications

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“…In fact, ELMOs are molecular orbitals strictly localized on small molecular fragments (e.g., atoms, bonds and functional groups) and, for this reason, easily transferable from one molecule to another, provided that the environments of the subunit on which the transferred orbital is localized are approximately equivalent in the two systems. [101][102][103][104][105][106][107][108] The current version of the QM/ELMO technique presents common features both to the projection-based embedding approach [69][70][71][72][73][74][75][76][77][78][79] and to the well-known QM/MM strategy [36][37][38][39][40][41][42] . In fact, similarly to the PbE method (and particularly to its absolutely localized variant 75,76,94 ), frozen (extremely) localized molecular orbitals are used to describe the environment region and to embed/polarize the active subsystem.…”

Section: Introductionmentioning

confidence: 99%

QM/ELMO: A Multi-Purpose Fully Quantum Mechanical Embedding Scheme Based on Extremely Localized Molecular Orbitals

2021

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The development of computationally advantageous methods for the study of large systems is a long-standing research topic in theoretical chemistry. Among these techniques, a prominent place is certainly occupied by the multi-scale embedding strategies, from the well-known QM/MM (quantum mechanics / molecular mechanics) methods to the latest and promising fully quantum mechanical approaches. In this Feature Article, we will briefly review the recently proposed QM/ELMO (quantum mechanics / extremely localized molecular orbital) scheme, namely a new multiscale embedding strategy in which the most chemically relevant region of the investigated system is treated at fully quantum chemical level, while the remaining part (namely, the environment) is described by means of transferred extremely localized molecular orbitals that remain frozen throughout the computation. Other than highlighting the theoretical bases, here we will also review the main results obtained through all the currently available variants of the novel method. In particular, we will show how the QM/ELMO embedding scheme has been successfully exploited to perform both ground and excited state calculations, reproducing the results of corresponding fully quantum mechanical computations but with a much lower computational cost. A first application to crystallography will be also discussed and we will describe how the QM/ELMO approach has been recently coupled with the Hirshfeld atom refinement technique to accurately determine the positions of hydrogen atoms from X-ray diffraction data.Given the reliability and quality of the obtained results, future applications of the current versions of the QM/ELMO embedding strategy to different types of chemical problems are to be expected in the near future. Moreover, further algorithmic improvements and methodological developments are also envisaged, such as the development of a polarizable QM/ELMO scheme accounting for the effects of the QM

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Section: Introductionmentioning

confidence: 99%

QM/ELMO: A Multi-Purpose Fully Quantum Mechanical Embedding Scheme Based on Extremely Localized Molecular Orbitals

2021

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“…[34][35][36] ELMOs are molecular orbitals (MOs) strictly localized on small molecular subunits [37][38][39] (e.g., atoms, bonds or functional groups) and, due to their absolute localization, they can be easily and reliably transferred from one molecule to another. 34,35,[39][40][41][42][43][44] On the basis of this property, libraries of ELMOs have been constructed with the goal of almost instantaneously obtaining approximate wave function and electron densities of molecules ranging from small polypeptides to large proteins. 36 They have been also recently exploited to perform the first successful quantum mechanics-based refinements of crystal structures of relatively large biological molecules 45 in the context of quantum crystallography [46][47][48][49][50][51] and to develop the novel QM/ELMO (quantum mechanics / extremely localized molecular orbital) technique, [52][53][54] namely an embedding strategy in which the chemically active region of the system is treated at fully quantum chemical level, while the environment is described through transferred and frozen ELMOs.…”

Section: Introductionmentioning

confidence: 99%

A Step toward the Quantification of Noncovalent Interactions in Large Biological Systems: The Independent Gradient Model-Extremely Localized Molecular Orbital Approach

Wieduwilt

Boisson

Terraneo

et al. 2021

J. Chem. Inf. Model.

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The Independent Gradient Model (IGM) is a recent electron density-based computational method that enables to detect and quantify covalent and non-covalent interactions. When applied to large systems, the original version of the technique still relies on promolecular electron densities given by the sum of spherically-averaged atomic electron distributions, which leads to approximate evaluations of the inter-and intramolecular interactions occurring in systems of biological interest. To overcome this drawback and perform IGM analyses based on quantum mechanically rigorous electron densities also for macromolecular systems, we coupled the IGM approach with the recently constructed libraries of extremely localized molecular orbitals (ELMOs) that allow fast and reliable reconstructions of polypeptide and protein electron densities. The validation tests performed on small polypeptides and peptide dimers have shown that the novel IGM-ELMO strategy provides results that are systematically closer to the fully quantum mechanical ones and outperforms the IGM method based on the crude promolecular approximation, but still keeping a quite low computational cost. The results of the test calculations carried out on proteins have also confirmed the trends observed for the IGM analyses conducted on small systems. This makes us envisage the future application of the novel IGM-ELMO approach to unravel complicated non-covalent interaction networks (e.g., in protein-protein contacts) or to rationally design new drugs through molecular docking calculations and virtual high-throughput screenings.

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“…and the remaining part through frozen extremely localized molecular orbitals [59][60][61] (ELMOs) that are exported from suitable databanks [62][63][64] or tailor-made model molecules. In fact, being orbitals strictly localized on small molecular subunits (e.g., atoms, bonds or functional groups), ELMOs are reliably transferable from a molecule to another [62][63][64][65][66][67][68][69] As already stated above, here the focus will be on the TDDFT/ELMO technique, which underwent most of the validation tests that were conceived to assess performances and capabilities of the LR-TD-EMFT method 43 and of the absolutely localized PBE strategy for excited-states 54 . We wanted to prove that the new approach is able i) to describe local excited-states in large systems also when the partition between the QM and ELMO subunits occurs across covalent bonds, ii) to eliminate the typical spurious low-lying charge-transfer states of TDDFT, iii) to provide accurate results when sufficiently large parts of biological systems are considered as chemically active regions in the calculations.…”

Section: Introductionmentioning

confidence: 99%

Quantum Mechanics / Extremely Localized Molecular Orbital Embedding Strategy for Excited-States. 1. Coupling to Time-Dependent Density Functional Theory

Macetti¹,

Genoni²

2020

Preprint

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The QM/ELMO (quantum mechanics / extremely localized molecular orbital) method is a recently developed embedding technique in which the most important region of the system under exam is treated at fully quantum mechanical level, while the rest is described by means of transferred and frozen extremely localized molecular orbitals. In this paper, we propose the first application of the QM/ELMO approach to the investigation of excited-states and, in particular, we present the coupling of the QM/ELMO philosophy with Time-Dependent Density Functional Theory (TDDFT). The proposed TDDFT/ELMO strategy has been subjected to a series of preliminary tests that were already considered for the validations of other embedding TDDFT methods. The obtained results show that the novel technique allows the accurate description of local excitations in large systems by only including a relatively small group of atoms in the region treated at fully quantum chemical level. Furthermore, it was observed that, even using functionals that do not take into account long-range corrections, the method enables to avoid the presence of artificial low-lying charge-transfer states that may affect traditional TDDFT calculations. Finally, through the application to a reduced model of the Green Fluorescent Protein, it was proved that the TDDFT/ELMO approach can be also successfully exploited to investigate local electronic transitions in large systems and that the accuracy of the results can be improved by including a sufficient number of fragments/residues that are chemically crucial in the quantum mechanical region. This work paves the way to further extensions of the QM/ELMO philosophy for the study of local excitations in extended systems, suggesting the coupling of the QM/ELMO approach with other quantum chemical methods for excited-states, from the simplest ΔSCF techniques to the most advanced and computationally expensive multi-references methods.

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A Hylleraas functional based perturbative technique to relax the extremely localized molecular orbital wavefunction

Cited by 16 publications

References 56 publications

QM/ELMO: A Multi-Purpose Fully Quantum Mechanical Embedding Scheme Based on Extremely Localized Molecular Orbitals

QM/ELMO: A Multi-Purpose Fully Quantum Mechanical Embedding Scheme Based on Extremely Localized Molecular Orbitals

A Step toward the Quantification of Noncovalent Interactions in Large Biological Systems: The Independent Gradient Model-Extremely Localized Molecular Orbital Approach

Quantum Mechanics / Extremely Localized Molecular Orbital Embedding Strategy for Excited-States. 1. Coupling to Time-Dependent Density Functional Theory

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