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  • 1
    Electronic Resource
    Electronic Resource
    Vibronic interactions in the C36 tri- and tetra-anions (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 10088-10092 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We address the intramolecular vibronic interactions in the C36 tri- and tetra-anions to understand the Jahn–Teller effects and possible superconductivity in "electron-doped" C36 solids. We use the B3LYP hybrid Hartree–Fock/density-functional-theory method for our theoretical analyses. Neither the highest occupied molecular orbital (HOMO) nor the lowest unoccupied molecular orbital (LUMO) of the C36 molecule with D6h symmetry are degenerate, but the next LUMO is twofold degenerate. One can therefore expect Jahn–Teller distortions and interesting electronic properties in the C36 anions. Computed vibronic and electron–phonon coupling constants of the tetra-anion are about twice as large as those of the tri-anion. The second lowest Jahn–Teller active E2g mode of 561 cm−1 is predicted to have the largest coupling constants in both anions. We calculate superconducting transition temperature Tc from McMillan's formula using the coupling constants as well as electronic densities of states at the Fermi level and Coulomb pseudopotentials as parameters. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480359
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  • 2
    Electronic Resource
    Electronic Resource
    A second-order effect causing the layer structure of arsenic (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11534-11541 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The role of second-order perturbations in the interlayer interactions of gray arsenic is discussed. A hypothetical structural change from the germanium (or diamond) to the arsenic structures is considered using a two-layer model in terms of second-order Jahn–Teller distortions. We show from the concept of transition density or transition force that the second-order term originating from mixing of the pseudodegenerate bands near the Fermi level leads to the well-known layer structure of arsenic. The interesting structure of arsenic is a consequence of orbital interactions near the Fermi level. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479095
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  • 3
    Electronic Resource
    Electronic Resource
    Electron–phonon coupling in the one-dimensional crystals of negatively charged [18]annulene (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 8514-8520 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We discuss the Jahn–Teller effect and possible superconductivity in negatively charged [18]annulene, (CH)18, which is an interesting molecular system with a highly symmetric D6h geometry in the neutral state. Electron–phonon coupling constants in model one-dimensional crystals of (CH)18−, (CH)183−, (CD)18−, and (CD)183− are calculated and analyzed using the B3LYP density functional method of Becke and Lee, Yang, and Parr. The lowest two frequency modes (116 cm−1 and 405 cm−1) causing distortions of the C–C framework of [18]annulene and the highest frequency mode (3201 cm−1) of C–H stretching appear to give significant electron–phonon coupling constants. The computed coupling constants of the monoanion are larger than those of the trianion. Possible preconditions under which idealized one-dimensional crystals of (CH)18− and (CH)183− can exhibit superconductivity at finite temperature are considered. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477516
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  • 4
    Electronic Resource
    Electronic Resource
    Vibronic coupling and Jahn–Teller effect in negatively charged benzene and [18]annulene (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 7637-7644 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibronic (vibrational–electronic) interactions and Jahn–Teller distortions in the mono- and trianions of benzene and [18]annulene, which show delocalized D6h structures in their neutral states, are discussed. E2g modes of vibration remove the orbital degeneracies in these highly symmetric molecules to lead to D2h distortions. We calculate the electronic structures, vibrational modes, and linear vibronic coupling constants of benzene and [18]annulene as well as their deutero-forms using the B3LYP method, a hybrid (Hartree–Fock/density functional theory) method. The C–C stretching E2g mode of 1656 cm−1 and the C–H stretching E2g mode of 3184 cm−1 give large vibronic coupling constants in the mono- and trianions of benzene. On the other hand, in [18]annulene the lowest E2g mode of 116 cm−1 affords extremely large coupling constants in its mono- and trianions to contribute to the Jahn–Teller distortions. The lowest mode of [18]annulene is related to a deformation of the carbon ring of [18]annulene and analogous to acoustic mode of phonon in solid. Thus, the different types of E2g mode play an important role in the Jahn–Teller distortions in negatively charged benzene and [18]annulene. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476199
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  • 5
    Electronic Resource
    Electronic Resource
    Intrinsic reaction coordinate analysis of the conversion of methane to methanol by an iron–oxo species: A study of crossing seams of potential energy surfaces (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 538-545 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Crossing seams between the potential energy surfaces and possible spin inversion processes for the direct conversion of methane to methanol by the bare FeO+ species are discussed by means of the intrinsic reaction coordinate (IRC) approach. There are three crossing seams between the sextet and the quartet potential energy surfaces, and spin inversion should occur twice in the entrance and the exit channels; FeO+(6Σ+)+CH4(1A1)→OFe+(CH4)(6A)→TS1(4A′)→HO–Fe+–CH3(4A)→TS2(4A)→Fe+(CH3OH)(4A)→Fe+(6D)+CH3OH(1A′). The first crossing seam exists in prior to TS1, a four-centered transition state for the cleavage of a C–H bond of methane. This crossing seam is the most important aspect in this reaction pathway because the molecular system should change its spin multiplicity from the sextet state to the quartet state near this crossing region, leading to a significant decrease in the barrier height of TS1 from 31.1 to 22.1 kcal/mol at the B3LYP level of density functional theory. The second crossing seam occurs in the vicinity of the hydroxy intermediate (HO–Fe+–Ch3), but this crossing seam would not play a significant role because the quartet IRC valley always lies below the sextet one in this region of reaction coordinate and accordingly the molecular system would preferentially move on the quartet potential energy surface. The third crossing seam exists in the exit channel in which the elimination of methanol occurs from the product complex. This crossing seam will again lead to spin inversion from the quartet to the sextet state, by which the elimination energy can be decreased from 57.2 to 37.4 kcal/mol in the FeO+/CH4 system. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479333
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  • 6
    Electronic Resource
    Electronic Resource
    Jahn–Teller effects in the coronene anions and cations (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 249-255 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibronic (vibrational–electronic) interactions and Jahn–Teller distortions in the mono- and trianions and the mono- and trications of coronene are discussed. E2g modes of vibration remove the orbital degeneracies in the highly symmetric D6h molecule to lead to D2h distortions. We calculate and analyze the vibrational modes and the linear vibronic coupling constants of the anions and cations of coronene as well as its deutero-form using the (Becke and Lee, Yang, and Parr) density-functional method. Although there are twelve E2g modes of vibration in coronene, some of them appear to play a significant role in the Jahn–Teller distortions. The lowest frequency mode of 370 cm−1, the C–C stretching mode of 1668 cm−1, and the C–H stretching modes of 3177 and 3193 cm−1 give large coupling constants in the anions. In particular, the 1668 cm−1 mode plays the most important role in the Jahn–Teller distortions both in the anions and cations. There is electron–hole symmetry in the coupling constants in the anions and cations. We also demonstrate an important H/D isotope effect. The highest two C–H stretching modes are important for the Jahn–Teller distortions in coronene; however, the corresponding C–D stretching modes are less important for the Jahn–Teller distortions in deutero-coronene. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478100
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic properties of polymers based on thienothiadiazole and thiophene (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5528-5538 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio crystal orbital (CO) studies on the geometric and the electronic structures of poly(thienothiadiazole) (Poly-1a) and periodic copolymers of thienothiadiazole and thiophene with the ratio of 1:1 (Poly-2b) and 1:2 (Poly-3b) are presented. In Poly-1a and Poly-2b, considerable change in the geometries is found to occur as one moves from their oligomers to the polymers. Although thienothiadiazole oligomers have a very small highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) separation, the corresponding polymer (Poly-1a) has a considerably large band gap. On the contrary, the geometric and electronic structures of Poly-3b are almost identical to those of the oligomer, and Poly-3b possesses a direct band gap of 1.3 eV estimated by simple scaling. The reasons for these differences are discussed in terms of orbital interactions and nonbonding molecular orbitals in the oligomers, and the reduced π-conjugation and enhanced intercell interaction in the polymers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471792
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio study on quartet states of non-Kekulé-type molecules 1,3,5-trimethylenebenzene and 1,3,5-triaminobenzene trication (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4453-4458 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structures of non-Kekulé-type isoelectronic molecules 1,3,5-trimethylenebenzene (TMB) and 1,3,5-triaminobenzene trication (TAB3+) having a threefold axis are discussed with the ab initio molecular orbital (MO) method. The quartet state with a D3h geometry is predicted to be the ground state of TMB and TAB3+. According to the Jahn–Teller theorem, the doublet 2E‘ states of TMB and TAB3+ are subject to the first order distortions which remove the degeneracy. The quartet–doublet energy splittings are calculated for these non-Kekulé-type molecules at the second order Møller–Plesset (MP2) perturbation level of theory. In TMB the 4A2‘ state with a planar D3h geometry is predicted to lie well below the 2A2 state with a planar C2v geometry in which one of the methylene groups has a longer C–C bridge bond connecting with the benzene ring. Moreover, in TAB3+ the 4A2‘ state with a planar D3h geometry also lies well below the 2A2 state. The 2A2–2B1 energy splittings on the pseudorotation potential surface overestimated at the unrestricted Hartree–Fock (UHF) level are corrected with the MP2 method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466275
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  • 9
    Electronic Resource
    Electronic Resource
    n-Alkyl Group-Substituted Poly(m-aniline)s: Syntheses and Magnetic Properties (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 5618-5625 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00120a029
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  • 10
    Electronic Resource
    Electronic Resource
    Plasma polymerization of 1-benzothiophene (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5653-5660 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Semiconductive thin organic polymer films have been prepared by the plasma polymerization of 1-benzothiophene. Characteristics of the polymeric products such as their electrical conductivities, optical properties, and electron spin properties have been examined in detail. Doping of these films with iodine has resulted in an increase in electrical conductivity by eight to nine orders of magnitude. The molecular structure of the products has also been discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350181
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