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Molecular structures that permit intramolecular rotational motion have the potential to function as molecular rotors. We have employed density functional theory and vibrational frequency analysis to study the characteristic structure and vibrational behavior of the molecule (4′,4″″-(bicyclo[2,2,2]octane-1,4-diyldi-4,1-phenylene)-bis-2,2′:6′,2″-terpyridine. IR active vibrational modes were found that favor intramolecular rotation. To demonstrate the rotor behavior of the isolated single molecule, ab initio molecular dynamics simulations at various temperatures were carried out. This molecular rotor is expected to be thermally triggered via excitation of specific vibrational modes, which implies randomness in its direction of rotation. [ABSTRACT FROM AUTHOR]

The energetically favorable structures and characteristic infrared (IR) and Raman peaks of TinOm (n = 2--4, m<2n) clusters are obtained in this work using a B3LYP/6-311G(d) method of density functional theory (DFT). The structures with m < 2n compose of Ti atoms of lower numbers of coordination with O atoms, providing many dangling bonds which con-siderably enhance the reactivity compared with its bulk counterpart. Two- and three-coordi-nated O atoms present for m/n < 1.5, whereas two- and also single-coordinated O atoms are found for m/n > 1.5. The TinOm (n = 2--4, m < 2n) clusters show strong IR peaks in the range of 600-1100 cm-1 and strong Raman peaks in the region of 300-800 cm-1, whereas both the IR and Raman spectrum peaks of the TinOm (n = 2--4, m = 2n) clusters are in the region of 700--1100cm-1. The main Raman peak of the TinOm (m ≠ 2n) clusters is at a frequency considerably lower than that of the IR spectrum. Our results can help understand the structure-property relationships of the TinOm clusters and provide their characteristic spectroscope features for further experimental identification. [ABSTRACT FROM AUTHOR]

We propose a possible approach for controlled formation of various 585 (containing pentagonal and octagonal carbon rings) extended line defects (ELDs) by linear adsorption of various kinds of atoms (C, N, B, O) on a graphene substrate, based upon density functional theory and molecular-dynamics (MD) simulations. We find out that the C and N atoms spontaneously transform to 585 ELDs while other elements find specific stable configurations. To confirm the feasibility of forming the ELD from line adsorption, investigation of the critical transformation conditions of the 585 ELD is involved based upon various adsorption models and adsorption densities. [ABSTRACT FROM AUTHOR]

To provide useful information on dissociation of water molecule on (TiO2)n clusters for experimental verification, we have calculated the infrared (IR) and Raman spectra of three possible states involved, namely molecularly adsorbed state, metastable state and dissociatively adsorbed state, using density functional theory at the B3LYP/6-311G(d) level. We find that the characteristic bands of H2O molecules below 2000 cm-1 in both IR and Raman spectra vanish upon both molecular and dissociative adsorption of H2O. In the high frequency range of 3600-4200 cm-1, the adsorption caused the single IR peak of water to split into two bands, while the dissociation removed the one at lower frequency and blue shifted slightly the higher frequency band. The two Raman peaks of the water molecule in the same high frequency range were slightly blue shifted upon adsorption but the one at lower frequency was removed upon dissociation, while the one at high frequency blue shifted slightly. The intensities of vibrational modes of water in 3600-4200 cm-1 are generally significantly enhanced upon both molecular and dissociative adsorption. Our results show clearly signatures of dissociation of water molecule into hydroxyl radical at the terminal site. [ABSTRACT FROM AUTHOR]

We have implanted boron (B) ions (dosage: 5×1014 cm-2) into diamond and then hydrogenated the sample by implantating hydrogen ions at room temperature. A p-type diamond material with a low resistivity of 7.37mΩcm has been obtained in our experiment, which suggests that the hydrogenation of B-doped diamond results in a low-resistivity p-type material. Interestingly, inverse annealing, in which carrier concentration decreased with increasing annealing temperature, was observed at annealing temperatures above 600 °C. In addition, the formation mechanism of a low-resistivity material has been studied by density functional theory calculation using a plane wave method. [ABSTRACT FROM AUTHOR]

Abstract: We performed systematic first principles calculations based on density functional theory to probe the energetics of dissociation of water molecules on small (TiO2) n (n =3, 4, 6, 8, and 10) clusters. We found that the (TiO2) n clusters have a strong ability to adsorb water molecules and the dissociative adsorption of water molecules on the surface of (TiO2) n clusters with a three step process is irreversible, size-dependent and energetically more favorable than the same on the surfaces of titanium oxide. Charged (TiO2) n cluster also have strong ability in H2O molecule splitting similar as neutral ones. The efficiency of water molecules dissociating on (TiO2) n cluster surface varies inversely with the cluster size due to the steric effect. Our results indicate a higher efficiency of small clusters of titanium oxide in dissociating water molecules than its low index surfaces of bulk terminated. [Copyright &y& Elsevier]