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

The growth mechanisms of solid solutions crystallising from aqueous solutions

In this paper, we present a generalisation of the classical growth rate equations to the case of crystallisation in solid solution–aqueous solution (SS-AS) systems. In these new equations, basic growth parameters, interfacial free energy and supersaturation are functions of the solid composition. Therefore, each equation describes, for a given aqueous solution, a growth rate distribution as a function of the solid composition. Different crystal growth models such as two-dimensional nucleation or spiral growth mechanisms provide different growth rate distributions. We have studied the general behaviour of growth rate equations in solid solution–aqueous solution (SS-AS) systems. Finally, we have applied the generalised growth rate equations to the BaxSr1xSO4–H2O SS-AS system. It allowed us to determine relationships between growth mechanisms and solid composition in such a model system. The result of our calculations were discussed and compared with previous experimental work on the BaxSr1xSO4–H2O SS-AS system

The rational design, synthesis and demonstration of the recognition and binding of a diaza-dioxa-12-crown-4 diphosphonate macrocycle to all crystal growth faces of barium sulfate

Computer-aided molecular design and virtual screening of a series of amino phosphonic acid derivatives were used to probe the probable interaction of these compounds as potential crystal growth inhibitors of barium sulfate, as judged by their ability to bind efficiently to all of the possible growing faces. As a result, a diphosphonic acid derivative of a 1,7-dioxa-4,10-diaza-12-crown-4 system 5 was proposed as a potential inhibitor of barium sulfate crystallisation. A subsequent synthesis of this macrocycle was developed, together with other larger-ring oxa-aza crown derivatives. Macrocycle 5 proved to be a highly efficient inhibitor of barium sulfate crystal growth at a level of 0.096 mM, as evidenced by the changes brought about in crystal morphology. Work was therefore undertaken to probe the mechanism of action of 5 using adsorption isotherms, mixed flow reactor and atomic force microscopy (AFM) measurements. It was possible to show that 5 inhibits effectively in solution by covering the growing surfaces, as observed on the 001 surface, effectively inhibiting two-dimensional nucleation as well as monolayer-step growth

Synthesis of LiNi0.5 Mn1.5 O4 cathode materials with different additives: Effects on structural, morphological and electrochemical properties

In this work, LiNi0.5 Mn1.5 O4 spinel type materials have been prepared by spray drying an aqueous solution of acetates and subsequent calcination of the dried precursors. Three different additives, namely polyvinylpyrrolidon (PVP), citric acid and urea have been used and their influences on the structure, morphology and electrochemical performance of the final cathode materials have been examined. Results show that the employed additives increase the purity of the disordered spinel phase and thus lead to higher discharge capacities. By the use of PVP and citric acid, a more stable cycling behavior and a better rate capability are achieved due to the well-controlled secondary particle morphology. Regarding the microstructural changes, flake-like secondary particle morphology has been observed for the use of PVP in the synthesis process, as in former work reported [J. Power Sources, 293, 137 (2015)]. The evolution of this structure is examined in more detail and possible way of formation is proposed

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

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