Entity

Time filter

Source Type


Pham-Tran N.-N.,Ho Chi Minh City University of Technology | Nguyen M.T.,Catholic University of Leuven | Nguyen M.T.,Institute for Computational Science and Technology of HoChiMinh City
Comptes Rendus Chimie | Year: 2010

A series of oligothiophenes and novel oligophospholes, consisting of fluorinated and perfluoroarene-substituted structures, were investigated using density functional theory (DFT) methods. The study focused on the geometrical structures and electronic properties. The degree of π-conjugation in the neutral oligomers was probed by different approaches including analysis of predicted Raman spectra. The character of the charge carrier of the new substituted oligomers, either electron (n-type doping) or hole (p-type doping) transport, was predicted by comparing their properties, including the frontier orbital HOMO and LUMO, excitation, and reorganization energies, with those of their non-substituted parent oligomers. The quantum chemical DFT results are consistent with available experimental data on the oligothiophenes for both geometries and conductivity properties. The results strongly suggest that an effective way of designing new materials with n-type conductivity is to introduce electron-withdrawing groups into the oligomer backbone. Calculated results were subsequently obtained for oligomers based on 1H-phospholes, which are predicted to have potentially useful properties as novel semiconductor materials. © 2010 Académie des sciences. Source


Tai T.B.,Catholic University of Leuven | Nhat P.V.,Catholic University of Leuven | Nguyen M.T.,Catholic University of Leuven | Nguyen M.T.,Institute for Computational Science and Technology of HoChiMinh City
Physical Chemistry Chemical Physics | Year: 2010

Quantum chemical calculations are performed on the aluminium doped lithium clusters LinAl at both neutral and cationic states using the DFT/B3LYP and CCSD(T) methods in conjugation with the aug-cc-pVaZ (a = D,T,Q) basis sets. The global minima are located and the growth mechanism is established. The electronic structure, geometrical parameters and energetic properties, such as average binding energy Eb, second difference of energy Δ2E, adiabatic and vertical ionization energy, and dissociated enthalpy, are evaluated using the coupled-cluster CCSD(T) method, whose energies are extrapolated to the complete basis set limit (CBS). The high stability of Li5Al, Li7Al, Li6Al+ and Li8Al+ that have the "magic numbers" of valence electrons, can be understood using the phenomenological shell model. © 2010 the Owner Societies. Source


Tai T.B.,Catholic University of Leuven | Nguyen M.T.,Catholic University of Leuven | Nguyen M.T.,Institute for Computational Science and Technology of HoChiMinh City
Chemical Physics Letters | Year: 2010

Structure and stability of the Ge12Mx clusters with M = Li, Na, Be, Mg, B, Al, and x from-1 to +1, each containing 50 valence electrons are investigated using DFT calculations. The global minima turn to be the high symmetry icosahedral structures, with large HOMO-LUMO gaps and high detachment or ionization energies. In particular, Li is found for the first time to be located at the center of an icosahedron Ge12Li-. The high thermodynamic stability of the icosahedra arises from a combination of their closed crystal field shells, spherical aromaticity and electrostatic attraction force. © 2010 Elsevier B.V. All rights reserved. Source


Lin L.,Catholic University of Leuven | Nguyen M.T.,Catholic University of Leuven | Nguyen M.T.,Institute for Computational Science and Technology of HoChiMinh City
Chemical Physics Letters | Year: 2010

CO oxidation on Au2n- (n = 1 - 4) cluster anions are investigated using DFT methods. O 2 prefers to bind on-top to a gold atom. Binding energies of O 2 on Au2n- are in the range of 0.8-1.2 eV. CO molecule can then insert into the O-O bond of Au2nO2- to form carbonate species, that are the most stable Au2nCO3- isomers, and thus expected to play an important role in CO oxidation. The negative charges of the gold carbonates are mainly distributed on the CO 3 moieties. The gold carbonate anions can yield CO 2 by direct dissociation or react with another CO to produce 2(CO 2). © 2010 Elsevier B.V. All rights reserved. Source


Lin L.,Catholic University of Leuven | Lievens P.,Catholic University of Leuven | Nguyen M.T.,Catholic University of Leuven | Nguyen M.T.,Institute for Computational Science and Technology of HoChiMinh City
Chemical Physics Letters | Year: 2010

CO adsorption on AunY (n = 1-9) is investigated using density functional theory, and compared with pure gold clusters Aun +1. CO is confirmed to prefer on-top binding to the least coordinated Au atom for the pure gold clusters, whereas for Y-doped gold clusters, the most favorable sites are dependent on the cluster size; the Au on-top sites are favored from n = 6. CO behaves as an electron acceptor, and the C-O vibrational frequency of the metal-CO complexes correlates with the degree of charge transfer to CO. Reactivity with CO is decreased after one gold atom is replaced by one yttrium for most sizes. © 2010 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations