| 671. |
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| 672. |
- Pinsook, U., et al.
(författare)
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Internal vibrations of the Li(NH3)(4)(+) complex analyzed from ab initio, density functional theory, and the classical spring network model
- 2008
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 112:24, s. 5323-5326
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Tidskriftsartikel (refereegranskat)abstract
- We report our theoretical findings regarding internal vibrations of the Li(NH3)(4)(+) complex which have been studied using three different methods, namely, a classical spring network model, density functional theory, and ab initio Hartree-Fock plus Moller-Plesset correlation energy correction truncated at second-order. The equilibrium Li center dot center dot center dot N and N center dot center dot center dot N distances are found to be 2.12 and 3.47 angstrom, respectively, in good agreement with the experimental data. The theoretically determined vibrational frequencies of the lowest modes are in good agreement with those extracted from inelastic X-ray scattering measurements. From group theory considerations, the internal vibrations of Li(NH3)(4)(+) complexes resemble those of a tetrahedral object. Further experimental investigation is suggested.
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| 673. |
- Pluengphon, Prayoonsak, et al.
(författare)
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Formation of Lightweight Ternary Polyhydrides and Their Hydrogen Storage Mechanism
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:3, s. 1723-1730
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Tidskriftsartikel (refereegranskat)abstract
- We have studied Na-Li-H compositions by mixing cations of Na and Li under high pressure using ab initio random structure searching and cluster expansion techniques. We have found that high pressure induces the structural stability of Na3LiH12, Na2Li2H12, and NaLi3H12 compounds. Our phonon calculations confirm the dynamical stability of these compounds, whereas our elastic constant calculations confirm their mechanical stability. Convex hull at 25 GPa indicates the minimum of relative enthalpy in Na2Li2H12, which is the new discovery at lower pressure than other alkali-polyhydride substances. The thermodynamic stability with respect to temperature is analyzed using quasi-harmonic oscillation approximation. Furthermore, NaLiH6 exhibits a high gravimetric hydrogen capacity, which makes this material a potential hydrogen storage candidate. We have also reported the formation enthalpy of hydrogen vacancies as well as the hydrogen diffusion in this lightweight ternary polyhydride system for its practical use in energy storage application.
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| 674. |
- Pluengphon, Prayoonsak, et al.
(författare)
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TM dopant-induced H-vacancy diffusion kinetics of sodium-lithium alanates : Ab initio study for hydrogen storage improvement
- 2022
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Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 47:43, s. 18763-18771
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Tidskriftsartikel (refereegranskat)abstract
- We present a hydrogen storage mechanism of the surface and bulk NaeLieAl hydrides substituted by the transition metal (TM) dopants such as Ni, Cu, Ag, and Zn. The host hydrides of interest, namely, NaAlH4, LiAlH4, Na3AlH4, Li3AlH4, and Na2LiAlH4 are found to be stable compositions at ambient pressure. Hydrogen vacancy mechanisms of the host hydrides with the TM dopants are investigated using ab initio calculations. Remarkably, the results show the enhancement of the internal mechanism for hydrogen storage in the Na-Li-Al complex hydrides. Doping of Ni or Zn mainly reduces the energy barrier of diffusion kinetics in the host Na-Li-Al hydrides, leading to the improvement of the hydrogen storage efficiency of the host Na-Li-Al hydrides. Therefore, hydrogen vacancy diffusion kinetics in the Na-Li-Al hydrides can be induced by adding the Ni and Zn dopants. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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| 675. |
- Poonia, Ekta, et al.
(författare)
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Aero-gel based CeO2 nanoparticles : synthesis, structural properties and detailed humidity sensing response
- 2019
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 7:18, s. 5477-5487
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present aero-gel based cerium oxide (CeO2) nanoparticles for the relative humidity (%RH) sensing application. X-ray diffraction (XRD) and N-2 adsorption-desorption isotherms revealed that the synthesized CeO2 nanoparticles (NPs) possessed a face centered cubic (fcc) structure with a high surface area (268 m(2) g(-1)). The high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and selected area electron diffraction (SAED) studies confirmed that the shape of CeO2 NPs was spherical and they possessed a polycrystalline nature. X-ray photoelectron spectroscopy (XPS) studies revealed the presence of both trivalent (Ce3+) and tetravalent (Ce4+) oxidation states of ceria. The CeO2 NPs' response towards %RH was explored by measuring the important sensing attributes (response/recovery, linearity, hysteresis, repeatability and stability) at 11-98%RH and at room temperature. An impressive impedance change of 4.5 orders of magnitude was observed along with a swift response (4.6 s) time and rapid recovery (2.7 s) time. Moreover, the prepared sensor showed negligible hysteresis, excellent stability and good reversible response in the complete 11-98%RH range.
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| 676. |
- Prasongkit, Jariyanee, et al.
(författare)
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Conductance of linear carbon wires bridging carbon nanotubes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The cumulenes bridging two-dimensional electrodes provide a model for interconnecting molecular electronics circuit with one of the most conductive molecular wires known. In recent experiments cumulene molecules bridging graphene sheets were observed [PRL 102, 205501 (2009)], thus demonstrating the mechanical way of producing cumulenes. Appearance of carbon wires: cumulenes and polynes, is also feasible between graphene sheets or carbon nanotubes (CNTs). In this work, we study structure and conductance of these wires suspended between CNTs of different chirality (zigzag and armchair), and graphene sheets (infinite radii CNTs) and corresponding conductance variation upon stretching. We find the geometrical structures of the carbon wire bridging CNT similar to the experimentally observed in the carbon wires obtained between graphene electrodes. We show a capability to modulate the conductance by changing bridging sites between the carbon wire and CNT without breaking the wire. Observed current modulation via cumulene wire stretching/elongation together with CNT stability makes it a promising candidate for mechano-switching device in molecular nanoelectronics.
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| 677. |
- Prasongkit, Jariyanee, et al.
(författare)
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Cumulene molecular wire conductance from first principles
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 81:11
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Tidskriftsartikel (refereegranskat)abstract
- We present first principles calculations of current-voltage characteristics (IVC) and conductance of Au(111):S-2-cumulene-S-2:Au(111) molecular wire junctions with realistic contacts. The transport properties are calculated using full self-consistent ab initio nonequilibrium Green's function density-functional theory methods under external bias. The conductance of the cumulene wires shows oscillatory behavior depending on the number of carbon atoms (double bonds). Among all conjugated oligomers, we find that cumulene wires with odd number of carbon atoms yield the highest conductance with metalliclike ballistic transport behavior. The reason is the high density of states in broad lowest unoccupied molecular orbital levels spanning the Fermi level of the electrodes. The transmission spectrum and the conductance depend only weakly on applied bias, and the IVC is nearly linear over a bias region of +/- 1 V. Cumulene wires are therefore potential candidates for metallic connections in nanoelectronic applications.
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| 678. |
- Prasongkit, Jariyanee, et al.
(författare)
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Highly Sensitive and Selective Gas Detection Based on Silicene
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:29, s. 16934-16940
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in the fabrication of silicene devices have raised exciting prospects for practical applications such as gas sensing. We investigated the gas detection performance of silicene nanosensors for four different gases (NO, NO2, NH3, and CO) in terms of sensitivity and selectivity, employing density functional theory and nonequilibrium Greens function method. The structural configurations, adsorption sites, binding energies and charge transfer of all studied gas molecules on silicene nanosensors are systematically discussed in this work. Our results indicate that pristine silicene exhibits strong sensitivity for NO and NO2, while it appears incapable of sensing CO and NH3. In an attempt to overcome sensitivity limitations due to weak van der Waals interaction of those latter gas molecules on the device, we doped pristine silicene with either B or N atoms, leading to enhanced binding energy as well as charge transfer, and subsequently a significant improvement of sensitivity. A distinction between the four studied gases based on the silicene devices appears possible, and thus these promise to be next-generation nanosensors for highly sensitive and selective gas detection.
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| 679. |
- Prasongkit, Jariyanee, et al.
(författare)
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Interference effects in phtalocyanine controlled by H-H tautomerization: Potential two-terminal unimolecular electronic switch
- 2011
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 84:16, s. 165437-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the electrical transport properties of two hydrogen tautomer configurations of phthalocyanine (H(2)Pc) connected to cumulene and gold leads. Hydrogen tautomerization affects the electronic state of H(2)Pc by switching the character of molecular orbitals with the same symmetry close to the Fermi level. The near degeneracy between the HOMO and HOMO-1 leads to pronounced interference effects, causing a large change in current for the two tautomer configurations, especially in the low-bias regime. Two types of planar junctions are considered: cumulene-H(2)Pc-cumulene and gold-H(2)Pc-gold. Both demonstrate a prominent difference in molecular conductance between ON and OFF states. In addition, junctions with gold leads show pronounced negative differential resistance (NDR) at high bias voltage, as well as weak NDR at intermediate bias.
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| 680. |
- Prasongkit, Jariyanee, et al.
(författare)
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Mechano-switching devices from carbon wire-carbon nanotube junctions
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : APS. - 1098-0121 .- 1550-235X. ; 87:15, s. 155434-155442
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Tidskriftsartikel (refereegranskat)abstract
- Well-known conductive molecular wires, such as cumulene or polyyne, provide a model for interconnectingmolecular electronics circuits. In recent experiments, the appearance of carbon wire bridging between twodimensional electrodes, i.e., graphene sheets, was observed [C. Jinet al.,Phys. Rev. Lett.102, 205501 (2009)], thusdemonstrating a mechanical way of producing cumulene. In this work, we studied the structure and conductanceof carbon wire suspended between carbon nanotubes (CNTs) of different chiralities (zigzag and armchair), andcorresponding conductance variation upon stretching. We found that the geometric structure of the carbon wirebridging CNTs was similar to the experimentally observed structures in carbon wire obtained between grapheneelectrodes. We show a way to modulate conductance by changing bridging sites between carbon wire and CNTswithout breaking the wire. Observed current modulation via cumulene wire stretching or elongation together withCNT junction stability makes this a promising candidate for use in mechano-switching devices for molecularnanoelectronics.
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