The labels for the two plots shown with triangles and for the horizontal dotted line (at 2.4 eV) in Figure 4(b) are incorrect: They refer to the Ce(4f )-Ce(5d) gap and not to the O(2p)-Ce(4f ) gap as stated. Correspondingly, the text passage below Fig. 4(b) should read: "The Ce(4f ) gap state however moves toward the valence band until it eventually overlaps the O(2p) valence band. For an intermediate value of U eff = 5 eV, the LDA+U method places the Ce(4f ) state approximately 1.7 eV below the Ce(5d) conduction band, compared to 2.4 eV measured experimentally. The GGA+U scheme predicts a somewhat bigger gap Ce(4f )-Ce(5d) of 2.1 eV for U eff = 5 eV." This, however, does not affect the general discussion.199906-1

It is demonstrated that the fluid-phase thermodynamics theory conductor-like screening model for real solvents (COSMO-RS) as implemented in the COSMOtherm software can be used for accurate and efficient screening of coformers for active pharmaceutical ingredient (API) cocrystallization. The excess enthalpy, H(ex) , between an API-coformer mixture relative to the pure components reflects the tendency of those two compounds to cocrystallize. Thus, predictive calculations may be performed with decent effort on a large set of molecular data in order to identify potentially new cocrystal systems. In addition, it is demonstrated that COSMO-RS theory allows reasonable ranking of coformers for API solubility improvement. As a result, experiments may be focused on those coformers, which have an increased probability of cocrystallization, leading to the largest improvement of the API solubility. In a similar way as potential coformers are identified for cocrystallization, solvents that do not tend to form solvates may be determined based on the highest H(ex) s with the API. The approach was successfully tested on tyrosine kinase inhibitor axitinib, which has a propensity to form relatively stable solvated structures with the majority of common solvents, as well as on thiophanate-methyl and thiophanate-ethyl benzimidazole fungicides, which form channel solvates.

Density functional plane-wave calculations have been performed to investigate a series of ceria nanoparticles (CeO2-x)(n), n Ce3+ reduction have been accounted for through the use of an effective on-site Coulomb repulsive interaction within the so-called DFT+U approach. Twelve nanoparticles of up to 2 nm in diameter and of both cuboctahedral and octahedral forms are chosen as representative model systems. Energetic and structural effects of oxygen vacancy formation in these nanoparticles are discussed with respect to those in the bulk and on extended surfaces. We show that the average interatomic distances of the nanoparticles are most significantly affected by the creation of oxygen vacancies. The formation energies of non-stoichiometric nanoparticles (CeO2-x)(n) are found to scale linearly with the average coordination number of Ce atoms; where x < 0 species, containing partially reduced O atoms, are less stable. The stability of octahedral ceria particles at small sizes, and the predicted strong propensity of Ce cations to acquire a reduced state at lower coordinated sites, is supported by interatomic potential-based global optimisations probing the low energy isomers of the Ce19O32 nanoparticle.

The electronic structure and properties of cerium oxides ͑CeO 2 and Ce 2 O 3 ͒ have been studied in the framework of the LDA+ U and GGA͑PW91͒ + U implementations of density functional theory. The dependence of selected observables of these materials on the effective U parameter has been investigated in detail. The examined properties include lattice constants, bulk moduli, density of states, and formation energies of CeO 2 and Ce 2 O 3 . For CeO 2 , the LDA+ U results are in better agreement with experiment than the GGA+ U results whereas for the computationally more demanding Ce 2 O 3 both approaches give comparable accuracy. Furthermore, as expected, Ce 2 O 3 is much more sensitive to the choice of the U value. Generally, the PW91 functional provides an optimal agreement with experiment at lower U energies than LDA does. In order to achieve a balanced description of both kinds of materials, and also of nonstoichiometric CeO 2−x phases, an appropriate choice of U is suggested for LDA+ U and GGA+ U schemes. Nevertheless, an optimum value appears to be property dependent, especially for Ce 2 O 3 . Optimum U values are found to be, in general, larger than values determined previously in a self-consistent way.

This paper discusses recent progress that has been made in the understanding of the electronic structure and bonding situation of carbon monoxide which was analyzed using modern quantum chemical methods. The new results are compared with standard models of chemical bonding. The electronic charge distribution and the dipole moment, the nature of the HOMO and the bond dissociation energy are discussed in detail.q

COSMO-RS theory can be applied to a range of physico-chemical properties, which are of interest in rational crystal engineering. Most notably, in combination with experimental reference data, accurate quantitative solubility predictions in any solvent or solvent mixture are possible. Additionally, COSMO-RS can be extended to the prediction of cocrystal formation, which results in considerable predictive accuracy concerning coformer screening. In a recent variant costly quantum chemical calculations are avoided resulting in a significant speed-up and ease-of-use.

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