Unraveling the performance of dispersion-corrected functionals for the accurate description of weakly bound natural polyphenols

Long-range non-covalent interactions play a key role in the chemistry of natural polyphenols. We have previously proposed a description of supramolecular polyphenol complexes by the B3P86 density functional coupled with some corrections for dispersion. We couple here the B3P86 functional with the D3 correction for dispersion, assessing systematically the accuracy of the new B3P86-D3 model using for that the well-known S66, HB23, NCCE31, and S12L datasets for non-covalent interactions. Furthermore, the association energies of these complexes were carefully compared to those obtained by other dispersion-corrected functionals, such as B(3)LYP-D3, BP86-D3 or B3P86-NL. Finally, this set of models were also applied to a database composed of seven non-covalent polyphenol complexes of the most interest.FDM acknowledges financial support from the Swedish Research Council (Grant No. 621-2014-4646) and SNIC (Swedish National Infrastructure for Computing) for providing computer resources. The work in Limoges (IB and PT) is supported by the “Conseil Régional du Limousin”. PT gratefully acknowledges the support by the Operational Program Research and Development Fund (project CZ.1.05/2.1.00/03.0058 of the Ministry of Education, Youth and Sports of the Czech Republic). IB gratefully acknowledges financial support from “Association Djerbienne en France”

Accurate Treatment of Large Supramolecular Complexes by Double-Hybrid Density Functionals Coupled with Nonlocal van der Waals Corrections

In this work, we present a thorough assessment of the performance of some representative double-hybrid density functionals (revPBE0-DH-NL and B2PLYP-NL) as well as their parent hybrid and GGA counterparts, in combination with the most modern version of the nonlocal (NL) van der Waals correction to describe very large weakly interacting molecular systems dominated by noncovalent interactions. Prior to the assessment, an accurate and homogeneous set of reference interaction energies was computed for the supramolecular complexes constituting the L7 and S12L data sets by using the novel, precise, and efficient DLPNO-CCSD(T) method at the complete basis set limit (CBS). The correction of the basis set superposition error and the inclusion of the deformation energies (for the S12L set) have been crucial for obtaining precise DLPNO-CCSD(T)/CBS interaction energies. Among the density functionals evaluated, the double-hybrid revPBE0-DH-NL and B2PLYP-NL with the three-body dispersion correction provide remarkably accurate association energies very close to the chemical accuracy. Overall, the NL van der Waals approach combined with proper density functionals can be seen as an accurate and affordable computational tool for the modeling of large weakly bonded supramolecular systems.Financial support by the “Ministerio de Economía y Competitividad” (MINECO) of Spain and European FEDER funds through projects CTQ2011-27253 and CTQ2012-31914 is acknowledged. The support of the Generalitat Valenciana (Prometeo/2012/053) is also acknowledged. J.A. thanks the EU for the FP7-PEOPLE-2012-IEF-329513 grant. J.C. acknowledges the “Ministerio de Educación, Cultura y Deporte” (MECD) of Spain for a predoctoral FPU grant

Synthesis of spinel LiNi0.5Mn1.5O4 with secondary plate morphology as cathode material for lithium ion batteries

Spinel LiNi0.5Mn1.5O4 material has been synthesized by a spray drying process and subsequent solid state reaction. Polyvinylpyrrolidone (PVP) is given as additive to the spray drying precursor solution and its effects on structural and electrochemical properties are evaluated. By using PVP in the synthesis process, the obtained sample displays a secondary plate morphology which is consisting of densely arranged primary octahedrally shaped particles. The new cathode material has a lesser degree of impurity phases, a higher discharge capacity, a superior rate capability, and a slightly better cycling performance than the sample synthesized without PVP. In more detail, by the use of PVP the ratio of Mn3+ to Mn4+ in the final product decreases from 20.8 to 9.2%. The initial discharge capacity at 0.1 C exhibits an increase of about 14%. The normalized capacity at 20 C is 84.1% instead of 67.0%. A slightly improved cycling performance with the capacity retention increase from 93.8 to 97.9% could be observed as well

Low-Cost Orthorhombic Nax[FeTi]O4 (x = 1 and 4/3) Compounds as Anode Materials for Sodium-Ion Batteries

Abundant and low-cost sodium, iron, and titanium have great potentials to act as raw materials for large-scale power sources. Here we report the synthesis of novel orthorhombic Nax[FeTi]O4 (x = 1 and 4/3) anode materials by a solid-state reaction method and their electrochemical behaviors in sodium-ion batteries. These materials are able to reversibly insert additional Na+ ions and show very good cycling stabilities. In particular, the Na4/3[FeTi]O4 material can deliver a high reversible capacity of 120 mA h g-1 at 0.1 C, and cyclic voltammetry (CV) investigation proves that there is no phase transformation during testing cycles. The Na[FeTi]O4 material exhibits an even higher initial charge capacity of 181 mA h g-1 at 0.1 C, and in situ X-ray diffraction (XRD) results indicate that Na+ ions behave in topotactic insertion and extraction manners inside this material. Meanwhile, gas evolutions during the initial redox process are analyzed by an operando mass spectrometry technique. The result suggests that the Na[FeTi]O4 material exhibits an enhanced safety

The effect of Sn substitution on the structure and oxygen activity of Na0.67Ni0.33Mn0.67O2 cathode materials for sodium ion batteries

A series of Na0.67Ni0.33Mn0.67-xSnxO2 (x = 0, 0.01, 0.03, 0.05) materials with mixed P2/P3 phases are synthesized with a conventional solid-state reaction method and investigated as cathode materials for sodium ion batteries. The effects of Sn substitution on the structure and electrochemical performance of the Na0.67Ni0.33Mn0.67O2 are systematically investigated. The substituted samples show smaller particle sizes compared to the pristine one and the P2:P3 phase ratio highly depends on the substitution amount. The best electrochemical performance is obtained by Na0.67Ni0.33Mn0.66Sn0.01O2, and it delivers a discharge capacity of 245 mA h g−1 in 1.5–4.5 V (vs. Na|Na+), which is the highest result for Na0.67Ni0.33Mn0.67O2 materials reported so far. The ex situ X-ray absorption spectroscopy and X-ray photoelectron spectroscopy measurements reveal that the oxygen ions participate in the redox reactions within the wide voltage range of 1.5–4.5 V. The increased capacity can be attributed to the smaller particle size, which results in more oxygen activity and then higher capacity