Asymmetric localization of titanium in carbon molecule (C28)

Dunlap, Brett I.; Haeberlen, Oliver D.; Roesch, Notker

doi:10.1021/j100202a003

Cited by 60 publications

(34 citation statements)

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“…The z-axis is collinear with the principal C 3 symmetry axis and the Ti atom is at a distance of 0.4579 Å from an origin placed at the center of nuclear charge (or 0.4533 Å from the center of mass). This equilibrium geometry is in good agreement with the results of Dunlap et al 51 In Table 4 we present the diagonal components of the static electronic dipole moment and linear polarizability, as well as the first and second hyperpolarizability of C 28 , C 28 H 4 and Ti@C 28 at the equilibrium geometry. Except, perhaps, for the linear polarizability we see that electron correlation, estimated at the MP2 level, often has a significant effect on the computed property.…”

Section: Clamped Nucleus Electronic Contributions To Electrical Propesupporting

confidence: 89%

Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C₂₈

et al. 2011

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The potential energy surface (PES) of Ti@C(28) has been revisited, and the stationary points have been carefully characterized. In particular, the C(2v) symmetry structure considered previously turns out to be a transition state lying 2.3 kcal/mol above the ground state of C(3v) symmetry at the MP2/6-31G(d) level. A large binding energy of 181.3 kcal/mol is found at the ROMP2/6-31G(d) level. Topological analysis of the generalized Ti@C(28) density reveals four bond paths between Ti and carbon atoms of the host. The character of all four contacts corresponds to a partially covalent closed shell interaction. UV-vis, IR, and Raman spectra are calculated and compared with C(28)H(4). The dipole moment and the static electronic and double harmonic vibrational (hyper)polarizabilities have been obtained. Distortion of the fullerene cage due to encapsulation leads to nonzero diagonal components of the electronic first hyperpolarizability β, and to an increase in the diagonal components of the electronic polarizability α and second hyperpolarizability γ. However, introduction of the Ti atom causes a comparable or larger reduction in most cases due to localized bonding interactions. At the double harmonic level, the average vibrational β is much larger than its electronic counterpart, but the opposite is true for α and for the contribution to γ that has been calculated. There is also a very large anharmonic (nuclear relaxation) contribution to β which results from a shallow PES with four minima separated by very low barriers. Thus, the vibrational γ (and α) may, likewise, become much larger when anharmonicity is taken into account.

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Section: Clamped Nucleus Electronic Contributions To Electrical Propesupporting

confidence: 89%

Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C₂₈

et al. 2011

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“…Using the same basis set as above we find the binding energy of Si 21 to be Ϫ4.40 eV/ atom. The large binding energy of this cluster is related to that of endohedral fullerene clusters 16 and very closely related to a novel Zr@Si 20 structure that was recently discovered. 17 The bonding in all these systems depends on a detailed match between the angular character of cage states near the Fermi level and the valence orbitals of the endohedral atom.…”

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confidence: 54%

Vibrational signatures for low-energy intermediate-sized Si clusters

et al. 1996

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We report low-energy locally stable structures for the clusters Si 20 and Si 21 . The structures were obtained by performing geometry optimizations within the local density approximation. Our calculated binding energies for these clusters are larger than any previously reported for this size regime. To aid in the experimental identification of the structures, we have computed the full vibrational spectra of the clusters, along with the Raman and IR activities of the various modes using a recently developed first-principles technique. These represent, to our knowledge, the first calculations of Raman and IR spectra for Si clusters of this size. ͓S0163-1829͑96͒06227-3͔Interest in the properties of Si clusters has grown in recent years, both as a result of the drive toward design and miniaturization in the electronics industry, and due to the many interesting and surprising properties of atomic clusters that have emerged from early experimental work.1 A crucial problem in this area involves the structure of the intermediate-sized clusters. The lowest-energy structures for small Si clusters (Nр13͒ appear well established by calculations 2-4 and for Nр10, experimental Raman spectra have confirmed these geometries. 5 At the other end of the size spectrum, large clusters are expected to take on bulklike structures. Between these limits, the structures of the intermediate-sized clusters are not known. The basic problem for theory is the complexity of the energy surfaces for these clusters and the vast number of local minima they are likely to contain. Various search strategies, coupled with a number of theoretical approaches, have been used to explore clusters in this size range, resulting in a wide variety of cluster models. [6][7][8][9][10][11][12] As was true for the clusters with Nр10, definitive identification of the structures is likely to come only through a combination of theory and experiment.In this paper we describe low-energy models for Si 20 and Si 21 , obtained using the local density approximation ͑LDA͒. These two structures have larger binding energies than alternative models that have appeared in the literature, making them leading candidates for minimum-energy structures. To further investigate the nature of these models and to encourage experimental work on clusters in this size range, we have computed the full vibrational spectrum for the clusters and the Raman and IR activities of the various modes. These calculations provide signatures that could be used to identify the clusters in experiments.The structures we report here were obtained using a standard conjugate-gradient algorithm with atomic forces calculated within the LDA. Our computational approach has been presented elsewhere. 15 Gaussian orbitals are used to represent the electronic states of the clusters and a numerical scheme is used to obtain accurate LDA forces and total energies. 15 The cluster geometries were relaxed until the largest force on every atom dropped below 0.001 hartree/ Bohr. Calculations performed here utilized a basis s...

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“…5,6 Numerous theoretical investigations show that the C 28 skeleton can be stabilized by forming endohedral fullerenes M@C 28 , where M atoms have M 4+ configuration ͑e.g., d-elements Ti, Zr, Mo, f-elements U, Pu, Ce, p-elements Si, Ge͒. [6][7][8][9][10] On the other hand, it was predicted that the saturation of free valences of the C 28 molecule radical can be realized through their linking with hydrogen, halogen atoms, alkyl groups or through their joining to form polymers, films or crystals. 6,11,12 The four unpaired electrons localized on the carbon atoms common to each set of four triplets of pentagons make the C 28 fullerene similar to an sp 3 -hybridized carbon atom.…”

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confidence: 99%

Hyperdiamond and hyperlonsdaleit: Possible crystalline phases of fullereneC28

2005

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Structures, energies of formation, electronic spectra and values of bulk moduli for crystalline modifications of small fullerene C 28 with space groups Fd3m and P63/ mmc are calculated at the density-functional based tight-binding level. Both solid phases of C 28 have very similar characteristics, which are compared with those of crystals of other small fullerenes-C 20 and C 36 . The important role of component of the C -C bounds on the properties are shown.

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Asymmetric localization of titanium in carbon molecule (C28)

Cited by 60 publications

References 2 publications

Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C₂₈

Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C₂₈

Vibrational signatures for low-energy intermediate-sized Si clusters

Hyperdiamond and hyperlonsdaleit: Possible crystalline phases of fullereneC28

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Asymmetric localization of titanium in carbon molecule (C28)

Cited by 60 publications

References 2 publications

Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C28

Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C28

Vibrational signatures for low-energy intermediate-sized Si clusters

Hyperdiamond and hyperlonsdaleit: Possible crystalline phases of fullereneC28

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Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C₂₈

Electronic Structure, Bonding, Spectra, and Linear and Nonlinear Electric Properties of Ti@C₂₈