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  • AIP Publishing  (6)
  • 1
    Online Resource
    Online Resource
    Designing field-controllable graphene-dot-graphene single molecule switches: A quantum-theoretical proof-of-concept under realistic operating conditions
    AIP Publishing ; 2015
    In:  The Journal of Chemical Physics Vol. 143, No. 24 ( 2015-12-28)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 143, No. 24 ( 2015-12-28)
    Abstract: A theoretical proof of the concept that a particularly designed graphene-based moletronics device, constituted by two semi-infinite graphene subunits, acting as source and drain electrodes, and a central benzenoid ring rotator (a “quantum dot”), could act as a field-controllable molecular switch is outlined and analyzed with the density functional theory approach. Besides the ideal (0 K) case, we also consider the operation of such a device under realistic operating (i.e., finite-temperature) conditions. An in-depth insight into the physics behind device controllability by an external field was gained by thorough analyses of the torsional potential of the dot under various conditions (absence or presence of an external gating field with varying strength), computing the torsional correlation time and transition probabilities within the Bloembergen-Purcell-Pound formalism. Both classical and quantum mechanical tunneling contributions to the intramolecular rotation were considered in the model. The main idea that we put forward in the present study is that intramolecular rotors can be controlled by the gating field even in cases when these groups do not possess a permanent dipole moment (as in cases considered previously by us [I. Petreska et al., J. Chem. Phys. 134, 014708-1–014708-12 (2011)] and also by other groups [P. E. Kornilovitch et al., Phys. Rev. B 66, 245413-1–245413-7 (2002)] ). Consequently, one can control the molecular switching properties by an external electrostatic field utilizing even nonpolar intramolecular rotors (i.e., in a more general case than those considered so far). Molecular admittance of the currently considered graphene-based molecular switch under various conditions is analyzed employing non-equilibrium Green’s function formalism, as well as by analysis of frontier molecular orbitals’ behavior.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.4937411
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 2
    Online Resource
    Online Resource
    Exploring the possibilities to control the molecular switching properties and dynamics: A field-switchable rotor-stator molecular system
    AIP Publishing ; 2011
    In:  The Journal of Chemical Physics Vol. 134, No. 1 ( 2011-01-07)
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    In: The Journal of Chemical Physics, AIP Publishing, Vol. 134, No. 1 ( 2011-01-07)
    Abstract: A bistable, dipolar stator-rotor molecular system-candidate for molecular electronics is investigated. We demonstrate that it is possible to control the intramolecular torsional states and dynamics in this system by applying an appropriate additional electric field (instead of biasing one), achieving fine tuning and modulation of the relevant properties. The electric field effects on the quantities responsible for torsional dynamics (potential energy surface, potential barrier height, quantum and classical transition probabilities, correlation time, HOMO-LUMO gap) are studied from first principles. Our results indicate that it is possible to artificially stabilize the metastable conformational state of the studied molecule. The importance of this is evident, as the current-voltage characteristics of the metastable state are clearly distinguishable from the current-voltage characteristics of the two stable states. We report for the first time exact calculations related to the possibilities to control the thermally induced stochastic switching, and reduce the noise in a practical application. Thus, we believe that the molecule studied in this paper could operate as a field-switchable molecular device under real conditions.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.3519638
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2011
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 3
    Online Resource
    Online Resource
    Solvation of fluoroform and fluoroform–dimethylether dimer in liquid krypton: A theoretical cryospectroscopic study
    AIP Publishing ; 2013
    In:  The Journal of Chemical Physics Vol. 139, No. 5 ( 2013-08-07)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 139, No. 5 ( 2013-08-07)
    Abstract: A hybrid, sequential statistical physics–quantum mechanical electronic–quantum mechanical nuclei approach has been applied to study the C–H stretching frequencies of bare fluoroform dissolved in liquid krypton under cryogenic conditions (at ∼130 K), as well as upon blue shifting hydrogen bonding interactions with dimethylether in the same solvent. The structure of the liquid at 130 K was generated by Monte Carlo simulations of cryogenic Kr solutions containing either fluoroform or fluoroform and dimethylether molecules. Statistically uncorrelated configurations were appropriately chosen from the equilibrated MC runs and supermolecular clusters containing solute and solvent molecules (either standalone or embedded in the “bulk” part of the solvent treated as a polarizable continuum) were subjected to quantum mechanical electronic (QMel) and subsequent quantum mechanical nuclei (QMnuc) calculations. QMel calculations were implemented to generate the in-liquid 1D intramolecular C–H stretching vibrational potential of the fluoroform moiety and subsequently in the QMnuc phase the corresponding anharmonic C–H stretching frequency was computed by diagonalization techniques. Finally, the constructed vibrational density of states histograms were compared to the experimental Raman bands. The calculated anharmonic vibrational frequency shifts of the fluoroform C–H stretching mode upon interaction with dimethylether in liquid Kr are in very good agreement with the experimental data (20.3 at MP2 level vs. 16.6 cm−1 experimentally). Most of this relatively large frequency blue shift is governed by configurations characterized by a direct C–H⋯O contact between monomers. The second population detected during MC simulations, characterized by reversed orientation of the monomers, has a minor contribution to the spectral appearance. The experimentally observed trend in the corresponding bandwidths is also correctly reproduced by our theoretical approach. Solvation of the fluoroform monomer, according to experiment, results in small C–H stretching frequency red shift (∼−2 cm−1), while our approach predicts a blue shift of about 10 cm−1. By a detailed analysis of the anharmonic C–H stretching frequency dependence on the position of the nearest solvent krypton atom and also by analyzing the vibrational Stark effect induced by the local fluctuating field component parallel to the C–H axis, we have derived several conclusions related to these observations. The frequency vs. C⋯Kr distance dependence shows appreciable fluctuations and even changes in sign at R values close to the maximum of the C⋯Kr radial distribution function, so that most of the first-shell Kr atoms are located at positions at which the CH frequency shifts acquire either small negative or small positive values. It so happens, therefore, that even the actual sign of the frequency shift is strongly dependent on the correct description of the first solvation shell around CF3H by the Monte Carlo method, much more than the other in-liquid properties calculated by similar approaches.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.4816282
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 4
    Online Resource
    Online Resource
    On the nature of blueshifting hydrogen bonds: Ab initio and density functional studies of several fluoroform complexes
    AIP Publishing ; 2003
    In:  The Journal of Chemical Physics Vol. 119, No. 1 ( 2003-07-01), p. 313-324
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 119, No. 1 ( 2003-07-01), p. 313-324
    Abstract: Potential energy hypersurfaces (PESs) for four fluoroform complexes (with acetonitrile, ethyleneoxide, formaldehyde, and water) were explored at the HF, MP2, and B3LYP/6-311++G(d,p) levels of theory. Anharmonic C–H stretching vibrational frequency shifts are reported for all minima located on the studied PESs. In all cases, the lowest-energy minimum occurs for a C–H⋯O(N) hydrogen-bonded arrangement and is characterized by a significant C–H frequency blueshift (upshift), while additional minima [for “reversed” orientations, in which there is no direct C–H⋯O(N) contact] show only small C–H frequency upshifts. The large blueshifts found for the hydrogen-bonded arrangements are predominantly caused by the electronic exchange interaction, as revealed by Kitaura–Morokuma (KM) analysis, while the purely electrostatic+polarization interaction leads to C–H frequency redshifts, which was proven both by the KM analysis and the charge field perturbational (CFP) approach. The large net blueshifting effect of the exchange contribution is only possible thanks to the smallness of the redshifting electrostatic+polarization contribution, which, in turn, is a consequence of the fact that dμ(0)/drCH is negative for the fluoroform molecule. In all cases the charge transfer as well as the dispersion energy contributions lead to frequency redshifts. The small C–H blueshifts for the reversed orientations are almost completely governed by the electrostatic interaction, as shown by the KM and CFP analyses. All these characteristics of blueshifting H bonds are in line with a previously outlined general model concerning “standard” and “blueshifting” H-bonding interactions [K. Hermansson, J. Phys. Chem. A 106, 4695 (2002)] .
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1571517
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2003
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 5
    Online Resource
    Online Resource
    Different structures give similar vibrational spectra: The case of OH− in aqueous solution
    AIP Publishing ; 2013
    In:  The Journal of Chemical Physics Vol. 138, No. 6 ( 2013-02-14)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 138, No. 6 ( 2013-02-14)
    Abstract: We have calculated the anharmonic OH−(aq) vibrational spectrum in aqueous solution with a “classical Monte Carlo simulation + QM/MM + vibrational” sequential approach. A new interaction model was used in the Monte Carlo simulations: a modified version of the charged-ring hydroxide-water model from the literature. This spectrum is compared with experiment and with a spectrum based on CPMD-generated structures, and the hydration structures and H-bonding for the two models are compared. We find that: (i) the solvent-induced frequency shift as well as the absolute OH− frequency are in good agreement with experiment using the two models; (ii) the Raman and IR bands are very similar, in agreement with experiment; (iii) the hydration structure and H-bonding around the ion are very different with the two ion-water interaction models (charged-ring and CPMD); (iv) a cancellation effect between different regions of the hydration shell makes the total spectra similar for the two interaction models, although their hydration structures are different; (v) the net OH− frequency shift is a blueshift of about +80 cm−1 with respect to frequency of the gas-phase ion.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.4775589
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 6
    Online Resource
    Online Resource
    Al 3 + , Ca2+, Mg2+, and Li+ in aqueous solution: Calculated first-shell anharmonic OH vibrations at 300 K
    AIP Publishing ; 2010
    In:  The Journal of Chemical Physics Vol. 133, No. 17 ( 2010-11-07)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 133, No. 17 ( 2010-11-07)
    Abstract: The anharmonic OH stretching vibrational frequencies, ν(OH), for the first-shell water molecules around the Li+, Ca2+, Mg2+, and Al3+ ions in dilute aqueous solutions have been calculated based on classical molecular dynamics (MD) simulations and quantum-mechanical (QM) calculations. For Li+(aq), Ca2+(aq), Mg2+(aq), and Al3+(aq), our calculated IR frequency shifts, Δν(OH), with respect to the gas-phase water frequency, are about −300, −350, −450, and −750 cm−1, compared to −290, −290, −420, and −830 cm−1 from experimental infrared (IR) studies. The agreement is thus quite good, except for the order between Li+ and Ca2+. Given that the polarizing field from the Ca2+ ion ought to be larger than that from Li+(aq), our calculated result seems reasonable. Also the absolute OH frequencies agree well with experiment. The method we used is a sequential four-step procedure: QM(electronic) to make a force field+MD simulation+QM(electronic) for point-charge-embedded Mn+ (H2O)xfirst shell (H2O)ysecond shell (H2O)zthird shell clusters+QM(vibrational) to yield the OH spectrum. The many-body Ca2+-water force-field presented in this paper is new. IR intensity-weighting of the density-of-states frequency distributions was carried out by means of the squared dipole moment derivatives.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.3460261
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2010
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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