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Geometries and dissociation energies of water molecules on Aln (n = 2-25) clusters were investigated using density functional theory with all electron relativistic spin-polarized calculations under the generalized gradient approximation. An extensive structure search was performed to identify the low-energy conformations of AlnH2O complexes for each size. Optimal adsorption sites were assigned for low-energy isomers of the clusters. Size and site specific dependences were studied for the AlnH2O complexes in stabilities, geometries, adsorption energies, dissociation energies, Al-O bond lengths, and other characteristic quantities. The stabilities and geometries revealed that H atom in H2O is not inclined to bond with Al atoms. The most stable AlnH2O configurations for each size tend to correspond to the most stable bare Aln cluster except of Al6 and Al24 clusters. The HO bond lengths increase generally 0.01 Å with respect to the isolated H2O in all of the adsorption complexes. The dissociation energy of an isolated H2O into HO and H was 5.39 eV, which decreased about two-thirds to the energy range of 0.83-2.12 eV with the help of Aln clusters. In spite of the fluctuations, the dissociation energies of AlnH2O complexes rise with the size increasing as a whole. In addition, we also found that the bare Aln clusters with high vertical ionization potentials usually have high dissociation energies of H2O in the corresponding adsorption models. The energetically preferred spin-multiplicity of all the odd-n AlnH2O complexes is doublet, and it is singlet for all the even-n complexes with exception of Al2H2O which is triplet. [ABSTRACT FROM AUTHOR]

Abstract: The structure, stability and electronic properties of the different B-site partial substituted derivatives LaNi4.5M0.5 (M=Al, Mn, Fe, Co) have been investigated by means of the density functional theory using the full-potential linearized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The optimized results indicate that all of Al, Mn, Fe, Co atoms prefer to substitute Ni atoms in the 3g sites. Due to the different radius of elements, the cell volume would increase with the doping Ni (3g) atoms. And the sequence of volume is LaNi4.5Al0.5 >LaNi4.5Mn0.5 >LaNi4.5Fe0.5 >LaNi4.5Co0.5 >LaNi5, which is in agreement with the experimental result. The calculated data of formation and cohesive energies indicate that LaNi4.5Mn0.5 has the stablest structure among five alloys. Based on the analysis of the density of states and charge density, the interactions of Mn–Ni, Fe–Ni, Co–Ni atoms are greatly stronger compared to the Ni–Ni interaction, while the interaction of Al–Ni atoms is weakened. Based on the formation energy of hydrogen atom in LaNi4.5M0.5H0.5, the sequence of bounding hydrogen atoms is LaNi4.5Mn0.5 >LaNi4.5Fe0.5 >LaNi4.5Co0.5 >LaNi4.5Al0.5 >LaNi5. [Copyright &y& Elsevier]

The atomic structures, stabilities, electronic structures, and magnetic moments of neutral and singly positively and negatively charged SnnAl (n = 1–10) clusters are calculated with B3LYP/SDD method in density functional theory. Detailed analyses are implemented to acquire the properties of SnnAl(0, ±1) clusters, such as relative stabilities, electronic properties, natural population analyses, and magnetic moments. The calculation results show that the ground‐state structures of Sn2Al, Sn7Al, and Sn8Al clusters are different from those of Sn3, Sn8, and Sn9 clusters, the variation trend of binding energies of Snn + 1 and SnnAl(0, ±1) coincides, and the small kinks are the same. It is found that the changing tendency of the vertical electron detachment energies (VDEs) of Snn + 1 and SnnAl(0, ±1) is almost consistent with that of the adiabatic electron affinities (AEAs), except Sn8Al. Furthermore, the adiabatic ionization potential energies (AIPs) of SnnAl and Snn + 1 clusters exhibit oscillatory behavior, but the variation trend of SnnAl is contrary to that of Snn + 1 from n = 1 to n = 7. The simulation results indicate that SnnAl− and SnnAl+ display a similarity in the magnetic moments, when n = 1, 3, 4, 5, 6, 7, and 9. The charges are transferred from Al to Sn in Sn1–4Al. [ABSTRACT FROM AUTHOR]

Al17 clusters exhibit apparent changes in curvature, which resemble macroscopic metal tips. Here, we show, using the density functional theory method, how surface charges of Al17q (q = −2 to +3) ions affect the adsorption and dissociation behavior of HCl molecules. Geometries, adsorption energies, vibrational frequencies, Mulliken population analysis and transition states of (Al17HCl)q (q = −2 to +3) adsorption complexes were studied. The results revealed that HCl molecules tend to locate on tip sites of the Al17q (q = −2 to +3) ions. Anionic adsorption complexes are prone to H affinity adsorption, whereas cationic adsorption complexes favor Cl-affinity adsorptions. These adsorption behaviors look quite like macroscopic tip effects. H–Cl bonds of the adsorption complexes weaken with an increase in either positive or negative charge. Dissociation barriers of the H–Cl bonds exhibit binding energies that are 2 orders of magnitude smaller than those of an isolated HCl molecule. Considering adsorption energies and dissociation barriers comprehensively, HCl molecules should dissociate spontaneously for all the models considered. Generally, the more negative charges the clusters carry, the more energy the reaction will release. [ABSTRACT FROM AUTHOR]