@article {2677, title = {Chemistry of Single-Walled Carbon Nanotubes}, journal = {J. Comput. Theor. Nanosci.}, volume = {6}, number = {6}, year = {2009}, note = {ISI Document Delivery No.: 441BUTimes Cited: 0Cited Reference Count: 146Yeung, Charles See Tian, Wei Quart Liu, Lei Vincent Wang, Yan AlexanderSp. Iss. SI}, month = {Jun}, pages = {1213-1235}, type = {Review}, abstract = {

Single-walled carbon nanotubes (SWCNTs) have received significant attention from the scientific community over the past 15 years. Of particular interest is the potential of these macromolecules for use in molecular electronics, chemical sensory technology, nanobiology, and transition metal catalysis, For effective applications, the selective functionalization of the aforementioned all-carbon framework is necessary but has been met with considerable challenges. Herein, we review our approach to the exploration of structural and electronic properties of SWCNTs within density functional theory (DFT). Our investigations include mechanistic studies on chemical reactions of SWCNTs with defect and exploration of transition metal doped variants and their ability to adsorb small gas molecules.

}, keywords = {AB-INITIO, Defect, DOPED CARBON, ELECTRICAL-CONDUCTIVITY, ELECTROCHEMICALLY DEPOSITED FILMS, Electronic Structure, Gas Adsorption, GAUSSIAN-TYPE BASIS, GENERALIZED GRADIENT APPROXIMATION, LASER-ABLATION, MOLECULAR-ORBITAL METHODS, NANORODS, NITRIC-OXIDE, Nitrogen Monoxide, platinum, SIDEWALL FUNCTIONALIZATION, Single-Walled Carbon Nanotubes}, isbn = {1546-1955}, url = {://000265745100002}, author = {Yeung, C. S. and Tian, W. Q. and Liu, L. V. and Y. A. Wang*} } @article {2399, title = {Orientational order of near D-3h solutes in nematic liquid crystals}, journal = {Journal of Chemical Physics}, volume = {130}, number = {15}, year = {2009}, note = {ISI Document Delivery No.: 437KLTimes Cited: 2Cited Reference Count: 49Danilovic, Zorana Burnell, E. Elliott}, month = {Apr}, pages = {11}, type = {Article}, abstract = {Solutes that are similar in size, have a shape that is close to D-3h symmetry but contain dissimilar substituent groups (methyl versus chloro, contributing different electrostatic interactions to the anisotropic intermolecular potential), are used to delineate the short- and long-range anisotropic intermolecular interactions that lead to solute orientational order in nematic liquid crystals. The short-range interactions should be similar for all solutes and for D-3h symmetry should yield a single independent order parameter, whereas the long-range interactions are expected to differ with solute. Short-range size and shape mechanisms account for solute orientational order measured in magic mixtures (e.g., 55 wt \% ZLI-1132/N-p-ethoxybenzylidene-p({\textquoteright})-n-butylaniline), whereas additional mechanisms are required in other nematic liquid-crystal solvents. The results obtained for long-range interactions cannot be rationalized in detail using simple mean-field models that incorporate solute dipoles, quadrupoles, or polarizabilities. The results suggest that details of the solute electrostatics may need to be incorporated into the description of the anisotropic intermolecular potential.}, keywords = {AB-INITIO, ELECTRIC-FIELD GRADIENT, electrostatic, interactions, liquid crystals, LIQUID MIXTURES, liquid structure, MEAN TORQUE, molecular orientation, MOLECULAR-HYDROGEN, MONTE-CARLO SIMULATIONS, nematic, NMR, polarisability, POTENTIALS, SHAPE, SOLVENTS}, isbn = {0021-9606}, url = {://000265486300032}, author = {Danilovic, Z. and Burnell, E. E.} } @article {2689, title = {Perturbative total energy evaluation in self-consistent field Iterations: Tests on molecular systems}, journal = {J. Chem. Phys.}, volume = {130}, number = {14}, year = {2009}, note = {ISI Document Delivery No.: 439HCTimes Cited: 0Cited Reference Count: 24Zhang, Yu Adam Wang, Yan Alexander}, month = {Apr}, pages = {144116}, type = {Article}, abstract = {

The corrected Hohenberg-Kohn-Sham and corrected Harris total energy functionals recently proposed [B. Zhou and Y. A. Wang, J. Chem. Phys. 128, 084101 (2008)] have been generalized to the Hartree-Fock method. We have tested the functionals on a few molecular systems and found them to be very useful in accelerating the convergence of the total energy during a self-consistent field process.

}, keywords = {AB-INITIO, CRC, density, density functional theory, ELECTRON-GAS, EXTREMAL PROPERTIES, HF calculations, iterative methods, PERTURBATION THEORY, SCF calculations, SOLIDS, total energy}, isbn = {0021-9606}, url = {://000265617200018}, author = {Zhang, Y. A. and Y. A. Wang*} } @article {2392, title = {Theoretical study of the electronic spectra of s-triazine vapour}, journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie}, volume = {87}, number = {8}, year = {2009}, note = {ISI Document Delivery No.: 493VQTimes Cited: 3Cited Reference Count: 37Chong, Delano P.}, month = {Aug}, pages = {1148-1153}, type = {Article}, abstract = {The ionization and excitation spectra of valence and core electrons of s-triazine in the gas phase are studied with ab initio, density functional, and semi-empirical methods. The results are compared with available experimental data and previous calculations. New estimates are proposed for the ionization energies of both valence and core electrons. The calculated excitation energies are consistent with experiment.}, keywords = {AB-INITIO, AZINES, core-electron binding energies, DENSITY-FUNCTIONAL THEORY, DFT, electron spectra, ESCA, EXCHANGE-CORRELATION POTENTIALS, EXCITATION-ENERGIES, excitations, HYDROGEN, IONIZATION-POTENTIALS, ionizations, MOLECULAR CALCULATIONS, N-2, photoelectron spectra, s-triazine, SPECTROSCOPY, UV absorption}, isbn = {0008-4042}, url = {://000269766800008}, author = {Chong, D. P.} } @article {2319, title = {Adsorption of small gas molecules onto Pt-doped single-walled carbon nanotubes}, journal = {J. Phys. Chem. C}, volume = {112}, number = {19}, year = {2008}, note = {ISI Document Delivery No.: 297XATimes Cited: 15Cited Reference Count: 108Yeung, Charles See Liu, Lei Vincent Wang, Yan Alexander}, month = {May}, pages = {7401-7411}, abstract = {

The adsorption of small gaseous molecules to the metal center in Pt-doped (5,5) single-walled carbon nanotubes has been explored within density functional theory. A model system consisting of a single Pt atom residing in the middle of a carbon nanotube with capping H atoms is used for our investigation. For all gases studied, the overall process of adsorption was found to be exothermic, where the affinity strongly depended on the orientation of the molecule. By examining the density of states and molecular orbitals of these nanotube-adsorbate complexes in comparison to the bare Pt-doped nanotube, we show that the electronic structure of these materials is strongly influenced by the presence of gases. Hence, we propose an application of Pt-doped single-walled carbon nanotubes as gas sensors and hope to motivate experimental work in this field.

}, keywords = {AB-INITIO, COVALENT FUNCTIONALIZATION, ELECTRONIC-PROPERTIES, INTERMOLECULAR INTERACTIONS, LASER-ABLATION, NO, PLATINUM COMPLEXES, PT(111), SIDEWALL FUNCTIONALIZATION, TRANSITION-METAL}, isbn = {1932-7447}, url = {://000255649500014}, author = {Yeung, C. S. and Liu, L. V. and Y. A. Wang*} } @article {2281, title = {Structure and vibrational assignment of the enol form of 1-chloro-1,1 difluoro-pentane-2,4-dione}, journal = {J. Mol. Struct.}, volume = {878}, number = {1-3}, year = {2008}, note = {ISI Document Delivery No.: 300CGTimes Cited: 0Cited Reference Count: 42Tayyari, Sayyed Faramarz Najafi, Atefeh Afzali, Raheleh Emamian, Saeedreza Wang, Yan Alexander}, month = {Apr}, pages = {10-21}, type = {Article}, abstract = {

Molecular structure of 1-chloro-1,1-difluoro-pentane-2,4-dione (monochlorodifluoro-acetylacetone, CDFAA) has been investigated by means of ab initio and Density Functional Theory (DFT) calculations and the results were compared with those of 1,1,1-trifluoropentane-2,4-dione (trifluoro-acetylacetone, TFAA). The harmonic vibrational frequencies of the two most stable cis-enol forms were calculated at the 133LYP level of theory using 6-3 1 G** and 6-311 ++G** basis sets. We also calculated the anharmonic frequencies at the B3LYP/6-31G** level of theory for these two stable cis-enol isomers. The calculated frequencies and the Raman and IR intensities were compared with the experimental results. The energy difference between the two stable cis-enol forms, calculated at the MP2/6-31G** level, is only 3.42 U/mol. The observed vibrational frequencies and intensities in the gas phase are in excellent agreement with the corresponding values calculated for the two most stable conformers. However, the observed IR and Raman frequencies also indicate coexisting of both tautomers in the liquid phase and in solution. According to the theoretical calculations, at the B3LYP/6-31 1++G** level, the hydrogen bond strength for the most stable conformer is 54.45 U/mol, about 2.4 kJ/mol less than that of the corresponding conformer of TFAA. These results are in agreement with the obtained experimental data. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {1-chloro-1, 1-difluoro-pentane-2, 4-dione, AB-INITIO, anharmonicity, BETA-DIKETONES, density, ELECTRON-DIFFRACTION, ENERGY, EQUILIBRIUM, functional theory, HEXAFLUORO-ACETYLACETONE, intramolecular hydrogen bond, MALONALDEHYDE, MOLECULAR-STRUCTURE, TAUTOMERISM, vibrational spectra}, isbn = {0022-2860}, url = {://000255801300002}, author = {S. F. Tayyari* and Najafi, A. and Afzali, R. and Emamian, S. and Wang, Y. A.} } @article {1467, title = {Chemical reaction of nitric oxides with the 5-1DB defect of the single-walled carbon nanotube}, journal = {J. Phys. Chem. B}, volume = {110}, number = {5}, year = {2006}, note = {ISI Document Delivery No.: 011QXTimes Cited: 15Cited Reference Count: 39}, month = {Feb}, pages = {1999-2005}, type = {Article}, abstract = {

In this work, we applied a two-layered ONIOM (B3LYP/6-31G(d):UFF) method to study the reaction of nitric oxides with a 5-1DB defect on the sidewall of the single-walled carbon nanotube (SWCNT). We have chosen a suitable ONIOM model for the calculation of the SWCNT based on the analyses of the frontier molecular orbitals,, local density of states, and natural bond orbitals. Our calculations clearly indicate that the 5-1DB defect is the chemically active center of the SWCNT. In the reaction of nitric oxides with the defected SWCNT, the 5-1DB defect site can capture a nitrogen atom from nitric oxides, yielding the N-substitutionally doped SWCNT. We have explored the reaction pathway in detail. Our work verifies the chemical reactivity of the 5-1DB defects of the SWCNTs, indicates that the 5-1DB defect is a possible site for the functionalization of the SWCNTs, and demonstrates a possible way to fabricate position controllable substitutionally doped SWCNTs with a low doping concentration under mild conditions via some simple chemical reactions.

}, keywords = {AB-INITIO, BORON, chemisorption, density, DOPED CARBON, MOLECULAR-MECHANICS, NITROGEN, ONIOM, OPTIMIZATION, sensors}, isbn = {1520-6106}, url = {://000235284300009}, author = {Liu, L. V. and Tian, W. Q. and Y. A. Wang*} } @article {1466, title = {Ozonization at the vacancy defect site of the single-walled carbon nanotube}, journal = {J. Phys. Chem. B}, volume = {110}, number = {26}, year = {2006}, note = {ISI Document Delivery No.: 058DSTimes Cited: 11Cited Reference Count: 52}, month = {Jul}, pages = {13037-13044}, type = {Article}, abstract = {

The ozonization at the vacancy defect site of the single-walled carbon nanotube has been studied by static quantum mechanics and atom-centered density matrix propagation based ab initio molecular dynamics within a two-layered ONIOM approach. Among five different reaction pathways at the vacancy defect, the reaction involving the unsaturated active carbon atom is the most probable pathway, where ozone undergoes fast dissociation at the active carbon atom at 300 K. Complementary to the experiments, our work provides a microscopic understanding of the ozonization at the vacancy defect site of the single-walled carbon nanotube.

}, keywords = {AB-INITIO, DENSITY-MATRIX, ETHYLENE, FULLERENE, GAUSSIAN-ORBITALS, INITIO MOLECULAR-DYNAMICS, MECHANICS, OXYGEN, OZONE ADSORPTION, SIDEWALLS}, isbn = {1520-6106}, url = {://000238645700035}, author = {Liu, L. V. and Tian, W. Q. and Y. A. Wang*} } @article {1492, title = {XeCu covalent bonding in XeCuF and XeCuCl, characterized by Fourier transform microwave spectroscopy supported by quantum chemical calculations}, journal = {Journal of the American Chemical Society}, volume = {128}, number = {23}, year = {2006}, note = {ISI Document Delivery No.: 050PDTimes Cited: 28Cited Reference Count: 64}, month = {Jun}, pages = {7613-7621}, type = {Article}, abstract = {XeCu covalent bonding has been found in the complexes XeCuF and XeCuCl. The molecules were characterized by Fourier transform microwave spectroscopy, supported by MP2 ab initio calculations. The complexes were prepared by laser ablation of Cu in the presence of Xe and SF6 or Cl-2 and stabilized in supersonic jets of Ar. The rotational constants and centrifugal distortion constants show the XeCu bonds to be short and rigid. The Xe-131, Cu, and Cl nuclear quadrupole coupling constants indicate major redistributions of the electron densities of Xe and CuF or CuCl on complex formation which cannot be accounted for by simple electrostatic effects. The MP2 calculations corroborate the XeCu bond lengths and predict XeCu dissociation energies similar to 50- 60 kJ mol(-1). The latter cannot be accounted for in terms of induction energies. The MP2 calculations also predict valence molecular orbitals with significant shared electron density between Xe and Cu and negative local energy densities at the XeCu bond critical points. All evidence is consistent with XeCu covalent bonding.}, keywords = {AB-INITIO, DIPOLE MOMENTS, ELECTRIC-RESONANCE METHOD, GAUSSIAN-BASIS SETS, HYPERFINE CONSTANTS, KR, LASER-ABLATION, MOLECULAR CALCULATIONS, ROTATIONAL SPECTRA, VANDERWAALS COMPLEX}, isbn = {0002-7863}, url = {://000238099500051}, author = {Michaud, J. M. and Gerry, M. C. L.} } @article {1076, title = {Ground and first-excited global potential energy surfaces of the H2O+-He complex: Predictions of ion mobilities}, journal = {International Journal of Quantum Chemistry}, volume = {101}, number = {1}, year = {2005}, note = {ISI Document Delivery No.: 872KKTimes Cited: 2Cited Reference Count: 29}, month = {Jan}, pages = {1-7}, type = {Article}, abstract = {Ion mobilities of H2O+ drifting in helium are calculated and compared with experiment. These calculations employ global potential energy surfaces of the H2O+-He complex, which in the present case were calculated ab initio at the unrestricted MP2 level of theory using a basis set of aug-cc-pVTZ quality, and treating the ion as a rigid body. Details are presented of the general characteristics of both the ground and first-excited electronic states of the complex. Although only the ground-state surface was used for the mobility calculations, the ab initio determination of the ground state necessitated the inclusion of the first-excited state owing to the presence of a crossing between the two. This crossing is also described. Mobilities calculated from the global surfaces are in good agreement with experiment. (C) 2004 Wiley Periodicals, Inc.}, keywords = {AB-INITIO, COLLISIONAL ALIGNMENT, first-excited state, global energy, H2O+-He complex, HELIUM, INDUCED ROTATIONAL ALIGNMENT, ion mobility, MICROSOLVATION, MOLECULAR-DYNAMICS, MP2, SPECTRA, SUPERSONIC EXPANSIONS, SURFACE, VELOCITY, WATER CATION}, isbn = {0020-7608}, url = {://000225205900001}, author = {Chen, X. and Thachuk, M.} } @article {1245, title = {The quadrupole moment of the 3/2(+) nuclear ground state of Au-197 from electric field gradient relativistic coupled cluster and density-functional theory of small molecules and the solid state}, journal = {Journal of Chemical Physics}, volume = {122}, number = {12}, year = {2005}, note = {ISI Document Delivery No.: 915HDTimes Cited: 16Cited Reference Count: 109}, month = {Mar}, pages = {9}, type = {Review}, abstract = {An attempt is made to improve the currently accepted muonic value for the Au-197 nuclear quadrupole moment [+0.547(16)x10(-28) m(2)] for the 3/2(+) nuclear ground state obtained by Powers [Nucl. Phys. A230, 413 (1974)]. From both measured Mossbauer electric quadrupole splittings and solid-state density-functional calculations for a large number of gold compounds a nuclear quadrupole moment of +0.60x10(-28) m(2) is obtained. Recent Fourier transform microwave measurements for gas-phase AuF, AuCl, AuBr, and AuI give accurate bond distances and nuclear quadrupole coupling constants for the Au-197 isotope. However, four-component relativistic density-functional calculations for these molecules yield unreliable results for the Au-197 nuclear quadrupole moment. Relativistic singles-doubles coupled cluster calculations including perturbative triples [CCSD(T) level of theory] for these diatomic systems are also inaccurate because of large cancellation effects between different field gradient contributions subsequently leading to very small field gradients. Here one needs very large basis sets and has to go beyond the standard CCSD(T) procedure to obtain any reliable field gradients for gold. From recent microwave experiments by Gerry and co-workers [Inorg. Chem. 40, 6123 (2001)] a significantly enhanced Au-197 nuclear quadrupole coupling constant in (CO)AuF compared to free AuF is observed. Here, these cancellation effects are less important, and relativistic CCSD(T) calculations finally give a nuclear quadrupole moment of +0.64x10(-28) m(2) for Au-197. It is argued that it is currently very difficult to improve on the already published muonic value for the Au-197 nuclear quadrupole moment.}, keywords = {AB-INITIO, AUGMENTED-WAVE METHOD, CRYSTAL-STRUCTURE, DIRAC-FOCK, DOUGLAS-KROLL, GAUSSIAN-BASIS SETS, MICROWAVE-SPECTRA, MOSSBAUER-SPECTROSCOPY, POINT-CHARGE MODEL, PURE ROTATIONAL SPECTRA}, isbn = {0021-9606}, url = {://000228287900026}, author = {Schwerdtfeger, P. and Bast, R. and Gerry, M. C. L. and Jacob, C. R. and Jansen, M. and Kello, V. and Mudring, A. V. and Sadlej, A. J. and Saue, T. and Sohnel, T. and Wagner, F. E.} } @article {1014, title = {Mechanisms of Staudinger reactions within density functional theory}, journal = {J. Org. Chem.}, volume = {69}, number = {13}, year = {2004}, note = {ISI Document Delivery No.: 831IDTimes Cited: 25Cited Reference Count: 96}, month = {Jun}, pages = {4299-4308}, type = {Article}, abstract = {

The Staudinger reactions of substituted phosphanes and azides have been investigated by using density functional theory. Four different initial reaction mechanisms have been found. All systems studied go through a cis-transition state rather than a trans-transition state or a one-step transition state. The one-step pathway of the phosphorus atom attacking the substituted nitrogen atom is always unfavorable energetically. Depending on the substituents on the azide and the phosphane, the reaction mechanism with the lowest initial reaction barrier can be classified into three categories: (1) like the parent reaction, PH3 + N3H, the reaction goes through a cis-transition state, approaches a cis-intermediate, overcomes a PN-bond-shifting transition state, reaches a four-membered ring intermediate, dissociates N-2 by overcoming a small barrier, and results in the final products: N-2 and a phosphazene; (2) once reaching the cis-intermediate, the reaction goes through the N-2-eliminating transition state and produces the final products; (3) the reaction has a concerted initial cis-transition state, in which the phosphorus atom attacks the first and the third nitrogen atoms of the azide simultaneously and reaches an intermediate, and then the reaction goes through similar steps of the first reaction mechanism. In contrast to the previous predictions on the relative stability of the unsubstituted cis-configured phosphazide intermediate and the unsubstituted trans-configured phosphazide intermediate, the total energy of the substituted trans-configured phosphazide intermediate is close to that of the substituted cis-configured phosphazide intermediate. The preference of the initial cis-transition state reaction pathway is thoroughly discussed. The relative stability of the cis- and the trans-intermediates is explored and analyzed with the aid of molecular orbitals. The effects of substituents and solvent effects on the reaction mechanisms of the Staudinger reactions are discussed in detail.

}, keywords = {AB-INITIO, GAS-PHASE, GAUSSIAN-TYPE BASIS, GOLD(I) COMPLEXES, METAL-COMPLEXES, MOLECULAR-ORBITAL METHODS, ORGANIC-MOLECULES, PHOSPHINIMIDE COMPLEXES, TRIAZADIENYL FLUORIDE, X-RAY CRYSTAL}, isbn = {0022-3263}, url = {://000222187200003}, author = {Tian, W. Q. and Y. A. Wang*} } @article {4944, title = {Dipole-induced ordering in nematic liquid crystals. II. The elusive holy grail}, journal = {Journal of Chemical Physics}, volume = {113}, number = {8}, year = {2000}, note = {ISI Document Delivery No.: 345AGTimes Cited: 23Cited Reference Count: 47}, month = {Aug}, pages = {3452-3465}, type = {Article}, abstract = {Similar size and shape molecules with different electric multipoles are used to investigate effects of molecular dipole, quadrupole, and polarizability interactions on the average orientational order of solutes in nematic liquid crystals. Solutes are codissolved in the same sample tube so that the orientational ordering among solutes can be directly compared and analyzed using mean-field models. Permanent dipoles have a negligible influence on solute orientational order. Effects from molecular polarizability interactions could not be separated from short-range interactions. However, order parameters predicted from strong, short-range repulsive forces coupled with interactions between the solute quadrupole and the average electric field gradient felt by the solute are consistent with experimental values. For the nematic mixture 55 wt\% ZLI 1132 in EBBA [N-(pethoxybenzylidene)-p{\textquoteright}-n-butylaniline] the contribution to solute ordering from long-range electrostatic interactions is negligible. (C) 2000 American Institute of Physics. [S0021-9606(00)52232-6].}, keywords = {AB-INITIO, ELECTRIC-DIPOLE, HARD ELLIPSOIDS, MEAN TORQUE, MOLECULAR QUADRUPOLE-MOMENTS, MONTE-CARLO SIMULATIONS, NMR-SPECTRA, ORDER, ORIENTATIONAL, SOLUTES, SOLVENTS}, isbn = {0021-9606}, url = {://000088792800063}, author = {Syvitski, R. T. and Burnell, E. E.} }