We perform first-principles calculations to investigate the band structure, density of states, optical absorption, and the imaginary part of dielectric function of Cu, Ag, and Au-doped Furthermore, according to the calculated results, we propose the optical transition mechanisms of Cu, Ag, and Au-doped TiO 2 , respectively. Our results show that the visible light response of TiO 2 can be modulated by substitutional doping of Cu, Ag, and Au.
The structural, electronic, and magnetic properties of iridium clusters with sizes of n = 2-15 are investigated by employing the generalized gradient approximation of density functional theory. Simple cube evolution pattern is revealed for Ir(2-15) clusters, as predicted by previous reports. It is remarkable that for Ir(10), Ir(11) clusters, new generated isomers with higher stabilities relative to those reported in previous studies are obtained. The even-sized clusters are more stable than the odd-sized species. The Ir-Ir bonds in the cubic Ir(8) and Ir(12) clusters, which are considered as the basic units in the structural evolution present covalent character. Starting from n = 8, the magnetic moments of Ir(n) clusters decrease sharply. The moments of magnetic clusters show 5d characters. The reactive site selectivity of studied clusters with n = 5-15 is analyzed with condensed Fukui function. The capped atoms in certain clusters (Ir(9), Ir(10), Ir(11), and Ir(13)) generally show extraordinary activity for both nucleophilic and electrophilic attack.
Equilibrium geometries of AlnTi (n = 2-24) clusters were studied using density-functional theory with generalized gradient approximation. The resulting geometries showed that the titanium atom remains on the surface of clusters for n < 20 but is endohedrally doped from n = 20. This structural transition confirms the previous experiment results obtained by studying their abilities for argon physisorption (Lang, S. M.; Claes, P.; Neukermans, S.; Janssens, E. J. Am. Soc. Mass Spectrom.2011, 22, 1508). The average bond lengths, coordination numbers, relative stabilities, electronic properties, and other relevant properties were discussed. It was found that the doped titanium atoms strengthen the stabilities of the pure aluminum clusters. The coordination numbers of titanium atoms along with the average Al-Ti bond lengths undergo dramatic increases during the structural transition. The intra-atomic hybridization exists in both Ti and Al atoms, and charge transfer from Al atoms to Ti atom were found in these complexes, which should reflect the strength of Al-Ti interactions. Electronic structure analysis based on the partial density of states reveals stronger Al-Ti interactions for the endohedrally doped structures.
Eight kinds of density functionals named B3LYP, PBE1PBE, B1B95, BLYP, BP86, G96PW91, mPWPW91, and SVWN along with two different valence basis sets (LANL2DZ and CEP-121g) are employed to study the transition-metal dimers for the elements of group VIII. By comparing the equilibrium bond distances, vibrational frequencies, and dissociation energies of the ground state of these dimers with the available experimental values and theoretical data, we show that the "pure" DFT methods (G96PW91, BLYP, and BP86) with great-gradient approximation always give better results relative to the hybrid HF/DFT schemes (B3LYP, PBE1PBE, and B1B95). The striking case found by us is that the G96PW91 functional, which is not tested in previous systemic studies, always predicts the dissociation energy to be well. The Ru 2 and Os 2 dimers are sensitive to not only the functionals employed but also the valence basis sets adopted. The natural bond orbital population is analyzed, and the molecular orbitals of the unpaired electrons are determined. Furthermore, our results indicate that the s and d orbitals of these dimers always hybridize with each other except for Rh 2 and Pt 2 molecules. And by analyzing the electron configuration of the bonding atom, the dissociation limit of the ground state is obtained.The eight functionals symbolized as B3LYP, PBE0 (PBE1PBE), B1B95, BP86, BLYP, G96PW91, mPWPW91, and SVWN, respectively, were employed. In the first hybrid functional (B3LYP), the three parameter hybrid functional (B3) that was devised by Becke in 1993 [9] was combined with the correction functionals of Lee, Yang, and Parr (LYP) [10]. Two one-parameter hybrid functionals were also used. One was B1B95 which is devised by Becke [11], the other was the 1997 hybrid functional of Perdew, Burke, and Ernzerhof (PBE1PBE) [12]. More over, four functionals (BP86, BLYP, G96PW91, mPWPW91) with great-gradient approximation (GGA) were also constructed. In the BP86 and BLYP schemes, the Becke's 1988 functional (B) [13] was combined with the gradient corrections of Perdew (P86) [14] and the correction functionals of LYP [11], respectively. And the other two functionals within GGA is G96PW91 and mPWPW91 methods, which married the Perdew's 1991 gradient-corrected correlation functional [15] with the 1996 exchange functional of Gill [16] and the Barone's modified PW91 exchange functional [17], respectively. In addition, the local-spin density approximation (LSDA) scheme was used, denoted as SVWN, in which the Slater exchange functional [18, 19] along with Vosko et al.'s correlation functional [20] were introduced.Two different valence basis sets were tested in our calculation in order to get the optimal result. One was LANL2DZ that the effective core potential (ECP) and basis set with a double-zeta type were suggested by Los Alamos National Laboratory [21][22][23]. In this basis set, the ECP did not consider the relativistic effect for Fe, Co, and Ni atoms, but for the other atoms in group VIII it took account of scalar relativistic effect, including not only...
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