Density functional study of neutral and anionic AlO(n) and ScO(n) with high oxygen content

The electronic and geometrical structures of neutral and negatively charged AlO₅, AlO₆, AlO₇, AlO₈, AlO₉, AlO₁₀, AlO₁₁, AlO₁₂, AlO₁₅, AlO₁₆, and AlO₁₈ along with the corresponding series of ScO_n and ScO oxides were investigated using density functional theory with generalized gradient approximation. We found that these species possess geometrically stable isomers for all values of n = 5–12, 15, 16, 18 and are thermodynamically stable for n = 5–7. The species with n = 16 are found to be octa‐dioxides M(η¹‐O₂)₈ while the species with n = 15 and 18 are penta‐ozonides (η²‐O₃)M(η¹‐O₃)₄ and hexa‐ozonides M(η¹‐O₃)₆, respectively. Geometrical configurations of a number of the lowest total energy states of Al and Sc oxides are different. Especially, drastic differences are found for the anion AlO and ScO pairs at n = 9, 10, and 11. The Sc? O bonds are longer than the Al? O bonds by ≈0.2 Å, which, in turn, slightly affects the corresponding interoxygen bond lengths. The charges on metal atoms are close to +2e in both Al series and to +1.5e in both Sc series. As an extra electron is delocalized over ligands in the presence of a large positive charge on the metal atom of the anions, the electron affinity (EA) of the neutrals along with the ionization energies of the anions are large and exceed the EAs of the halogen atoms in a number of cases. © 2011 Wiley Periodicals, Inc. J Comput Chem 2011     

Study of the structure and stability of compounds PF n,n=1–5, and their anions by the density functional method

The electronic and geometrical structure of phosphorus fluorides PF_n, n = 1–5, and their singly-charged negative ions was calculated using the density functional method. Both the ground and low-lying excited states of the two series were considered. The structural parameters of neutral radicals PF₂, PF₄, and their anions were obtained for the first time. The adiabatic and vertical electron affinities (EA) of the neutral phosphorus fluorides, and the first ionization potentials of the anions were calculated. According to the calculation results, all the phosphorus fluorides have positive EA_ad, except for PF₃, which has an EA of about zero, and requires further investigation. The dissociation energies of both the neutral and negatively charged phosphorus fluorides were calculated through different channels. All the PF_n and PF _n ^– , n = 1–5, are stable in the gaseous phase. The PF^–, PF ₂ ^– , PF ₃ ^– , and PF ₅ ^– anions have excited states which are stable with respect to both the splitting off of an outer electron and to dissociation.Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2219–2232, October, 1992.     

The acidic domains of the Toc159 chloroplast preprotein receptor family are intrinsically disordered protein domains

Background  

The Toc159 family of proteins serve as receptors for chloroplast-destined preproteins. They directly bind to transit peptides, and exhibit preprotein substrate selectivity conferred by an unknown mechanism. The Toc159 receptors each include three domains: C-terminal membrane, central GTPase, and N-terminal acidic (A-) domains. Although the function(s) of the A-domain remains largely unknown, the amino acid sequences are most variable within these domains, suggesting they may contribute to the functional specificity of the receptors.     

The use of ionization energies of core electrons for determination of the geometrical structure in inorganic salts

Based on the results of calculations on the electronic structure of the LiNO₃ and TINO₃ molecules by the Discrete Variational X_α-method (DVM—X_α) it is concluded that experimental X-ray photoelectron spectra (XPS) may be used in the determination of the equilibrium structure of inorganic salts. This may be done in those cases where peaks corresponding to ionization from the core levels of bridge and terminal ligand atoms of an anion are resolved in XPS. It is shown that the splitting energy itself is determined mainly by the deformation of the anion geometry.     

Competition between linear and cyclic structures in monochromium carbide clusters CrCn- and CrCn (n = 2-8): a photoelectron spectroscopy and density functional study

Photoelectron spectroscopy (PES) is combined with density functional theory (DFT) to study the monochromium carbide clusters CrCn- and CrCn (n = 2-8). Well-resolved PES spectra were obtained, yielding structural, electronic, and vibrational information about both the anionic and neutral clusters. Experimental evidence was observed for the coexistence of two isomers for CrC2-, CrC3-, CrC4-, and CrC6-. Sharp and well-resolved PES spectra were observed for CrCn- (n = 4,6,8), whereas broad spectra were observed for CrC5- and CrC7-. Extensive DFT calculations using the generalized gradient approximation were carried out for the ground and low-lying excited states of all the CrCn- and CrCn species, as well as coupled-cluster calculations for CrC2- and CrC2. Theoretical electron affinities and vertical detachment energies were calculated and compared with the experimental data to help the assignment of the ground states and obtain structural information. We found that CrC2- and CrC3- each possess a close-lying cyclic and linear structure, which were both populated experimentally. For the larger CrCn- clusters with n = 4, 6, 8, linear structures are the overwhelming favorite, giving rise to the sharp PES spectral features. CrC7- was found to have a cyclic structure. The broad PES spectra of CrC5- suggested a cyclic structure, whereas the DFT results predicted a linear one.     

Periodic table of 3d-metal dimers and their ions

The ground states of the mixed 3d-metal dimers TiV, TiCr, TiMn, TiFe, TiCo, TiNi, TiCu, TiZn, VCr, VMn, VFe, VCo, VNi, VCu, VZn, CrMn, CrFe, CrCo, CrNi, CrCu, CrZn, MnFe, MnCo, MnNi, MnCu, MnZn, FeCo, FeNi, FeCu, FeZn, CoNi, CoCu, CoZn, NiCu, NiZn, and CuZn along with their singly negatively and positively charged ions are assigned based on the results of computations using density functional theory with generalized gradient approximation for the exchange-correlation functional. Except for TiCo and CrMn, our assignment agrees with experiment. Computed spectroscopic constants (r(e),omega(e),D(o)) are in fair agreement with experiment. The ground-state spin multiplicities of all the ions are found to differ from the spin multiplicities of the corresponding neutral parents by +/-1. Except for TiV, MnFe, and MnCu, the number of unpaired electrons, N, in a neutral ground-state dimer is either N(1)+N(2) or mid R:N(1)-N(2)mid R:, where N(1) and N(2) are the numbers of unpaired 3d electrons in the 3d(n)4s(1) occupation of the constituent atoms. Combining the present and previous results obtained at the same level of theory for homonuclear 3d-metal and ScX (X=Ti-Zn) dimers allows one to construct "periodic" tables of all 3d-metal dimers along with their singly charged ions.