Assessing Recent Time-Dependent Double-Hybrid Density Functionals on Doublet-Doublet Excitations.

This work is the first thorough investigation of time-dependent double-hybrid density functionals (DHDFs) for the calculation of doublet-doublet excitation energies. It sheds light on the current state-of-the-art techniques in the field and clarifies if there is still room for future improvements. Overall, 29 hybrid functionals and DHDFs are investigated. We separately analyze the individual impacts of the Tamm-Dancoff approximation (TDA), range separation, and spin-component/opposite scaling (SCS/SOS) on 45 doublet-doublet excitations in 23 radicals before concluding with an overarching analysis that includes and excludes challenging excitations with double-excitation or multireference character. Our results show again that so-called "nonempirical" DHDFs are outperformed by semiempirical ones. While the best assessed functionals are DHDFs, some of the worst are also DHDFs and outperformed by all assessed hybrids. SCS/SOS is particularly beneficial for range-separated DHDFs. Spin-scaled, range-separated DHDFs paired with the TDA belong to the best tested methods here, and we particularly highlight SCS-ωB2GP-PLYP, SOS-ωB2PLYP, SOS-ωB2GP-PLYP, SOS-ωB88PP86, SOS-RSX-QIDH, and SOS-ωPBEPP86. When comparing our functional rankings with previous studies on singlet-singlet and singlet-triplet excitations, we recommend TDA-SOS-ωB88PP86 and TDA-SOS-ωPBEPP86 as robust methods for excitation energies in general until further improvements have been achieved that surpass the chemical accuracy threshold for challenging open-shell excitations without increasing the computational effort.

Time-Dependent Long-Range-Corrected Double-Hybrid Density Functionals with Spin-Component and Spin-Opposite Scaling: A Comprehensive Analysis of Singlet-Singlet and Singlet-Triplet Excitation Energies.

Following the work on spin-component and spin-opposite scaled (SCS/SOS) global double hybrids for singlet-singlet excitations by Schwabe and Goerigk [ J. Chem. Theory Comput. 2017, 13, 4307-4323] and our own works on new long-range corrected (LC) double hybrids for singlet-singlet and singlet-triplet excitations [ J. Chem. Theory Comput. 2019, 15, 4735-4744 and J. Chem. Phys. 2020, 153, 064106], we present new LC double hybrids with SCS/SOS that demonstrate further improvement over previously published results and methods. We introduce new unscaled and scaled versions of different global and LC double hybrids based on Becke88 or PBE exchange combined with LYP, PBE, or P86 correlation. For singlet-singlet excitations, we cross-validate them on six benchmark sets that cover small to medium-sized chromophores with different excitation types (local-valence, Rydberg, and charge transfer). For singlet-triplet excitations, we perform the cross-validation on three different benchmark sets following the same analysis as in our previous work in 2020. In total, 203 excitations are analyzed. Our results confirm and extend those of Schwabe and Goerigk regarding the superior performance of SCS and SOS variants compared to their unscaled parents by decreasing mean absolute deviations, root-mean-square deviations, or error spans by more than half and bringing absolute mean deviations closer to zero. Our SCS/SOS variants are shown to be highly efficient and robust for the computation of vertical excitation energies, which even outperform specialized double hybrids that also contain an LC in their perturbative part. In particular, our new SCS/SOS-ωPBEPP86 and SCS/SOS-ωB88PP86 functionals are four of the most accurate and robust methods tested in this work, and we fully recommend them for future applications. However, if the relevant SCS and SOS algorithms are not available to the user, we suggest ωPBEPP86 as the best unscaled method in this work.

Analysis of Recent BLYP- and PBE-Based Range-Separated Double-Hybrid Density Functional Approximations for Main-Group Thermochemistry, Kinetics, and Noncovalent Interactions.

We investigate the effects of range separation of the exchange energy on electronic ground-state properties for recently published double-hybrid density functionals (DHDFs) with the extensive GMTKN55 database for general main-group thermochemistry, kinetics, and noncovalent interactions. We include the semiempirical range-separated DHDFs ωB2PLYP and ωB2GP-PLYP developed by our group for excitation energies, together with their ground-state-parametrized variants, which we denote herein as ωB2PLYP18 and ωB2GP-PLYP18. We also include the nonempirical range-separated DHDFs RSX-0DH and RSX-QIDH. For all six DHDFs, damping parameters for the DFT-D3 dispersion correction (and for its DFT-D4 variant) are presented. We comment on when the range-separated functionals can be more beneficial than their global counterparts and conclude that range separation alone is no guarantee for overall improved results. We observe that the BLYP-based functionals generally outperform the PBE-based functionals. We finally note that the best-performing DHDFs for GMTKN55 are still the semiempirical range-separated double hybrids ωDSD3-PBEP86-D4 and ωDSD72-PBEP86-D4, the former of which includes a third-order perturbative correlation term in addition to the more conventional second-order perturbation that DHDFs are based upon.

Global double hybrids do not work for charge transfer: A comment on "Double hybrids and time-dependent density functional theory: An implementation and benchmark on charge transfer excited states".

We comment on the results published by Ottochian et al. in J. Comput Chem. 2020, 41, 1242. Therein, the authors claim that the second-order, perturbative correlation correction applied to the time-dependent version of the PBE-QIDH global double-hybrid functional approximation (DHDFA) enables the description of charge-transfer (CT) excitations. Herein, we point out some inadvertent oversights related to what had already been previously known and achieved in the field of time-dependent DHDFAs. Exemplified for the same four systems that Ottochian et al. have used to analyze intermolecular CT excitations, we show how a systematic and unacceptably large redshift in global DHDFAs is rectified when using the latest long-range corrected DHDFAs published earlier in J. Chem. Theory Comput. 2019, 15, 4735.

Assessing the Tamm-Dancoff approximation, singlet-singlet, and singlet-triplet excitations with the latest long-range corrected double-hybrid density functionals.

We continue our work on the long-range corrected double-hybrid density functionals (LC-DHDFs) ωB2PLYP and ωB2GP-PLYP that we developed in the context of time-dependent (TD) Density Functional Theory (DFT) to enable the robust description of singlet-singlet excitations [M. Casanova-Páez, M. B. Dardis, and L. Goerigk, J. Chem. Theory Comput. 15, 4735 (2019)]. In our initial study, we only assessed the impact of a LC on BLYP-based DHDFs, and herein, we extend our understanding by providing the first test of PBE-based LC-DHDFs within the established TD-DHDF scheme. Moreover, this study is one of few that provides a direct comparison between TD-DHDFs and their faster Tamm-Dancoff-approximation variants (TDA-DHDFs). Most importantly, this is the first TDA-DHDF study since Grimme and Neese's TDA-B2PLYP [J. Chem. Phys. 127, 154116 (2007)] and the first work on TD-DHDFs that addresses singlet-triplet excitations. We show how the difference between TD-DHDFs and TDA-DHDFs is often negligible for singlet-singlet excitations, but how one has to apply TDA-DHDFs for triplet excitations. For both excitation types, the LC is beneficial to the BLYP-based DHDFs, but detrimental to the PBE-based ones. For local-valence and Rydberg excitations, ωB2PLYP and ωB2GP-PLYP as well as the global DHDF PBE-QIDH can be recommended. If a transition exhibits charge-transfer character, ωB2PLYP and ωB2GP-PLYP should be applied. An analysis of the gaps between the first singlet and triplet excited states of our systems revealed that there is room for further improvements to reach better robustness. Until that goal has been achieved, we recommend ωB2PLYP and ωB2GP-PLYP as some of the currently best TDA-DFT methods.

ωB2PLYP and ωB2GPPLYP: The First Two Double-Hybrid Density Functionals with Long-Range Correction Optimized for Excitation Energies.

Double-hybrid density functionals are currently the most accurate density functionals for ground-state properties and electronic excitations. Nevertheless, the lack of a long-range correction scheme makes them unreliable when it comes to long-range excitations. For this reason, we propose the first two time-dependent double-hybrid functionals with correct asymptotic long-range behavior named ωB2PLYP and ωB2GPPLYP. Herein, we demonstrate their excellent performance and show that they are the most accurate and robust time-dependent density functional theory methods for electronic excitation energies. They provide a balanced description of local-valence, Rydberg, and charge-transfer states. They are also able to tackle the difficult first two transitions in polycyclic aromatic hydrocarbons and show very promising results in a preliminary study on transition-metal compounds, exemplified for titanium dioxide clusters. This work shows that double hybrids can be systematically improved also for excitation energies, and further work in this field is warranted.

Semi-empirical or non-empirical double-hybrid density functionals: which are more robust?

The development of non-empirical double-hybrid density functionals (DHDFs) is a very active research area with the number of approaches in this field having increased rapidly. At the same time, there is a lack of published work that provides a fair assessment and comparison between non-empirical and semi-empirical DHDFs on an equal footing. Herein, we close this gap and present a thorough analysis of both classes of DHDFs on the large GMTKN55 benchmark database for general main-group thermochemistry, kinetics, and noncovalent interactions [Goerigk et al., Phys. Chem. Chem. Phys., 2017, 19, 32184-32215]. In total, 115 variations of dispersion-corrected and -uncorrected DHDFs are tested, which will be condensed to an in-depth assessment of 31 methods: 19 non-empirical and 12 semi-empirical DHDFs. As such, our study represents the largest DHDF study ever conducted and can serve as an important benchmark informing method developers and users alike. Our results show that semi-empirical DHDFs are the most robust density functional approximations and more reliable and accurate than non-empirical ones. In fact, some non-empirical approaches are even outperformed by hybrid approaches or even dispersion-corrected and -uncorrected MP2 and SCS-MP2. SOS0-PBE0-2-D3(BJ) is the only exception and the only non-empirical DHDF that we can safely recommend for general applicability. However, it is still outperformed by six semi-empirical DHDFs, of which we would like to particularly recommend the following five: ωB97X-2-D3(BJ), DSD-BLYP-D3(BJ), DSD-PBEP86-D3(BJ), B2NC-PLYP-D3(BJ), and B2GPPLYP-D3(BJ). Our findings seriously question current trends in the field and they highlight that novel strategies have to be found in order to outperform the currently best density functional theory methods on the market. We hope that our study can function as an important cornerstone inspiring such a change of direction in the field.

Ventilación no invasiva y oxigenoterapia de alto flujo en niños en salas de cuidados moderados. Experiencia en la Unidad de Cuidados Respiratorios Especiales Agudos del Hospital Pediátrico del CHPR durante 2013-2016 / Non-invasive ventilation and high-flow oxygen therapy in children in moderate care rooms. Experience at the Special Respiratory Acute Care at the CHPR from 2013 to 2016 / Ventilação não invasiva e oxigenoterapia de alto fluxo em crianças em consultórios de atenção de nível moderado. Experiência na Unidade de Cuidados Respiratórios Especiais Agudos do Hospital Pediátrico do CHPR durante 2013-2016

Resumen: Introducción: las infecciones respiratorias agudas bajas (IRAB) constituyen un importante problema de salud en invierno. El centro de referencia nacional en Uruguay ofrece a niños con IRAB ventilación no invasiva (VNI) y cánula nasal de alto flujo (CNAF) en cuidados moderados. Objetivo: describir las características clínicas, tratamiento y evolución de los niños asistidos en la Unidad de Cuidados Respiratorios Especiales Agudos (CREA) del Hospital Pediátrico de referencia nacional. Material y método: estudio retrospectivo, descriptivo. Se incluyeron todos los niños hospitalizados por IRAB asistidos en CREA que recibieron VNI y/o CNAF entre 1/1/13 y 31/12/16. Se revisaron historias clínicas. Variables: características clínicas, tratamientos, complicaciones, evolución y destino. Resultados: se asistieron 650 niños (348 con CNAF; 302 con VNI); sexo masculino 63% (407). Bronquiolitis 63% (406), se detectó virus respiratorio sincicial (VRS) en 60% (388). Media de edad en niños que recibieron CNAF 11 meses (9 días-108 meses); promedio duración de la técnica: 3 días. Requirieron ingreso a unidades de cuidados intensivos (UCI): 12% (43); asistencia ventilatoria mecánica (AVM): 6% (22). Media de edad en niños que recibieron VNI :12 meses (1-132 meses); media de duración de la técnica: 3 días. Requirieron ingreso a UCI 16% (49); AVM: 9,6% (29). No se registraron fallecimientos ni complicaciones graves. Conclusiones: el 85% de los niños completó su tratamiento en la Unidad CREA. El porcentaje de niños que requirió AVM fue bajo. La implementación de estas técnicas en cuidados moderados redujo la necesidad de ingreso a UCI y probablemente la necesidad de AVM.

Summary: Introduction: acute lower respiratory tract infections (LRTI) are a major health problem in winter. The National Reference Center in Uruguay offers children with LRTI, non-invasive ventilation (NIV) and high-flow nasal cannula (CNAF) in moderate care. Objective: to describe the clinical characteristics, treatment and evolution of the children assisted in Special Respiratory Care Acute (CREA unit), in a national pediatric reference hospital. Patients and methods: retrospective, descriptive study. All children hospitalized for LRTI assisted in CREA who received NIV and / or CNAF between 1/1/13 and 12/31/16 were included in the study. Clinical records were reviewed. Variables: clinical characteristics, treatment, complications, evolution and destination. Results: a total of 650 children were assisted (348 with CNAF, 302 with NIV); male sex 63% (407). Bronchiolitis 63% (406), Respiratory Syncytial Virus (RSV) was detected in 60% (388). Mean age in children receiving CNAF was 11 months (9 days - 108 months); mean duration of technique was 3 days. Required admission to intensive care unit (ICU): 12% (43); invasive ventilation (IV) 6% (22). Mean age in children receiving NIV 12 months (1-132 months); mean duration of technique 3 days. Required admission to the ICU 49 (16%); IV 29 (9.6%). There were no deaths or serious complications. Conclusions: 85% of this group of children completed their treatment in the CREA unit. The percentage of children who required IV was low. The implementation of these techniques in moderate care reduced the need to enter an ICU and the need for IV.

Resumo: Introdução: as infecções respiratórias agudas baixas (IRAB) são um importante problema de saúde no inverno. O centro de referência nacional no Uruguai oferece ventilação não invasiva (NIV) e cânula nasal de alto fluxo (CNAF) em cuidados moderados às crianças com IRAB. Objetivo: descrever as características clínicas, tratamento e evolução das crianças atendidas na Unidade Especial de Tratamento Respiratório Agudo (CREA) do Hospital de Referência Nacional de Pediatria. Pacientes e métodos: estudo retrospectivo, descritivo. No estudo foram incluídas todas as crianças hospitalizadas por causa da IRAB atendidas no CREA que receberam VNI e / ou CNAF entre 1/1/13 e 31/12/16. Foram revisadas as histórias clínicas. Variáveis: características clínicas, tratamentos, complicações, evolução e destino. Resultados: 650 crianças foram atendidas (348 com CNAF, 302 com NIV); sexo masculino 63% (407). Bronquiolite 63% (406), o Vírus Respiratório Sincicial (VRS) foi detectado em 60% (388). Idade média em crianças que receberam CNAF: 11 meses (9 dias-108 meses); Duração média da técnica: 3 dias. Necessidade para admissão nas unidades de terapia intensiva (UTI): 12% (43); assistência ventilatória mecânica (MAV) 6% (22). Idade média em crianças que receberam VNI: 12 meses (1-132 meses); duração média da técnica: 3 dias. Deveram ser admitidos na UTI: 16% (49); AVM 9,6% (29). Nenhuma morte ou complicações sérias foram registradas. Conclusões: 85% das crianças completaram o tratamento na unidade CREA. A porcentagem de crianças que necessitaram de AVM foi baixa. A implementação dessas técnicas em cuidados moderados reduziu a necessidade de internação na UTI e, provavelmente, a necessidade de MAV.