A density-functional study of the structural, electronic, magnetic, and vibrational properties of Ti 8C 12 metallocarbohedrynes

M. A. Sobhy, A. W. Castleman, J. O. Sofo

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Abstract

Calculations are presented for the structural, electronic, and vibrational properties of the different Ti8 C12 metallocarbohedrynes. (Please note that we adopt the name "metallocarbohedrynes" instead of " metallocarbohedrenes" to denote the acetylenic nature of C2 units in this class of clusters demonstrated by several contributions in literature.) The density-functional theory (DFT) calculations are performed with the all-electron projector augmented-wave method and generalized gradient approximation for the exchange-correlation functional. We study the seven low-energy isomers of the Ti8 C12 metallocarbohedrynes using spin-polarized DFT, where we find a correlation between the number of rotated carbon dimers and the cohesive energy of the structure. The electronic density of states (eDOS) show that C3ν, D 3d*, and D3d isomers are spin polarized. The partial eDOS shows that, depending on the dimer orientation, carbon atoms and a subgroup of the metal atoms form a covalent framework while other metal atoms are bonded to this framework more ionically. This picture is further supported by the charge density of the different structures, where we see that the Ti atoms with higher charge density show less contribution to the covalent bonding of the Ti-C framework. The vibrational spectra of the different structures are calculated using the frozen-vibration method. Also, we calculate the vibrational spectra of the C3ν and C2ν structures using molecular-dynamics simulations at two different temperatures. The results of the simulations demonstrate the local stability of the structures beyond the harmonic limit explored by the frozen-vibration method.

Original languageEnglish (US)
Article number154106
JournalJournal of Chemical Physics
Volume123
Issue number15
DOIs
StatePublished - Oct 15 2005

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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