Co-reporter:Sen Zhang, Xian-Zhen Meng, Li–Li Yu, Qi Dong, Wei Quan Tian
International Journal of Hydrogen Energy 2011 Volume 36(Issue 1) pp:606-615
Publication Date(Web):January 2011
DOI:10.1016/j.ijhydene.2010.09.075
As candidates for hydrogen storage materials, Ti-doped pyracylenes, with a carbon atom replaced with a Ti atom, have been studied with density functional theory based method. Ti-doped pyracylene III with the Ti atom lying on a pentagon is the most stable isomer with substitutional energy of 4.73 eV/mol. Up to three H2 molecules can be adsorbed on to the Ti atom through charge transfer and partially chemisorptions due to the partially filled d orbitals and positive charges on Ti. Totally seven H2 molecules can be adsorbed on Ti-doped pyracylenes with mixture of chemo- and physisorption. Charge polarization induced electrostatic attraction is one of the major driving forces for physisorption.
Co-reporter:Xi-Mao Li, Wei Quan Tian, Qi Dong, Xu-Ri Huang, Chia-Chung Sun, Lei Jiang
Computational and Theoretical Chemistry 2011 Volume 964(1–3) pp:199-206
Publication Date(Web):March 2011
DOI:10.1016/j.comptc.2010.12.026
Substitution of all 10 3d transition metal (TM) atoms in a [8, 0] zigzag single walled boron nitride nanotube (BNNT) has been investigated with density functional theory based methods. The TM atoms protrude to the exterior of the wall and may facilitate this site to react with an approaching molecular or atomic species. The substitution is site selective when the number of d electrons is less than five with major product of B-substituted BNNT. The substitution produces mixture of B- and N-substituted BNNT when the number of d electrons is larger than five. The doping of TM atoms induces certain impurity states within the band gap of the pristine BNNT, thereby reducing the band gap and affecting the conductivity of metal-doped BNNTs.
Co-reporter:Xian-Zhen Meng, Sen Zhang, Li-Li Yu, Xue-Qin Ran, Wei Quan Tian
Journal of Molecular Structure: THEOCHEM 2010 Volume 958(1–3) pp:122-132
Publication Date(Web):30 October 2010
DOI:10.1016/j.theochem.2010.07.038
The electronic isomerization arising from the switch of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) has been investigated within density functional theory. The switch of the HOMO and LUMO changes the electronic structures, thus the physicochemical properties of isomers. The predicted geometry, infrared spectra, and electronic spectra of fullerenes investigated show significant change upon electronic isomerization.
Co-reporter:Yan-Hong Cui;Wei Quan Tian;Ji-Kang Feng;De-Li Chen
Journal of Nanoparticle Research 2010 Volume 12( Issue 2) pp:429-438
Publication Date(Web):2010 February
DOI:10.1007/s11051-009-9651-9
Among all the 4478 classical isomers of C66, C66(Cs:0060) with the lowest number of pentagon–pentagon fusions was predicted to be the most stable isomer, followed by isomers C66(C2v:0011) and C66(C2:0083). The infrared spectra and aromaticity of the most stable isomers were predicted. The relative stabilities of C66 isomers change with charges or doping of metals. The structures and relative stabilities of the most stable metallofullerenes were delineated and compared with experiment. Sc2@C66(C2:0083) was predicted to be the most stable metallofullerene, although Sc2@C66(C2v:0011) was observed. Charge-transfer from Sc2 to the fused pentagons and the bonding between these two moieties significantly decrease the strain energies caused by the pair of fused pentagons thereby stabilizing the fullerene cage.
Co-reporter:Qi Dong, Xi Mao Li, Wei Quan Tian, Xu-Ri Huang, Chia-Chung Sun
Journal of Molecular Structure: THEOCHEM 2010 Volume 948(1–3) pp:83-92
Publication Date(Web):30 May 2010
DOI:10.1016/j.theochem.2010.02.024
The adsorption of a series of small gaseous molecules (O2, CO2, C2H4, C2H2, H2O, NH3) on the metal center in Pt-doped (5, 5) armchair single-wall BN nanotubes (BNNTs) has been explored within density functional theory. For all these gases studied, the overall process of adsorption was found to be exothermic, where the affinity correlates with the nature of the molecule adsorbed. Charge transfer is an important factor in changing the conductivity of analyte–substrate system. The two kinds of Pt-doped BNNTs exhibit different sensitivity and selectivity to gas molecules. The electronic structure of these materials is strongly influenced by the presence of gases, hence, application of Pt-doped single-wall BNNTs as gas sensors was proposed to motivate experimental trial.
Co-reporter:Qi Dong, Wei Quan Tian, De-Li Chen, Chia-Chung Sun
International Journal of Hydrogen Energy 2009 Volume 34(Issue 13) pp:5444-5448
Publication Date(Web):July 2009
DOI:10.1016/j.ijhydene.2009.04.053
With respect to density functional predictions, TM–methylidynes (TM = Sc, Ti, V, and Cr) bind high-density hydrogen at ambient conditions. TM–methylidyne complexes can adsorb up to seven hydrogen molecules. The predicted maximal retrievable hydrogen storage density is 16.7 wt% for ScCH, a record high value so far, larger than the 16.0 wt% for TiCH, 13.2 wt% for VCH, and 13.0 wt% for CrCH. Dimerization and oligomerization of scandium–methylidyne lower the hydrogen storage capacity to 9.2 wt% for the dimer and to 7.9 wt% for the hexamer. These predictions provide useful guidance for designing novel hydrogen storage materials with optimal gravimetry and kinetics and for devising possible schemes by which the hydrogen/host material interactions can be manipulated.
Co-reporter:Yan-Hong Cui, Wei Quan Tian, Ji-Kang Feng, Wei-Qi Li, Zi-Zhong Liu
Journal of Molecular Structure: THEOCHEM 2009 Volume 897(1–3) pp:61-65
Publication Date(Web):15 March 2009
DOI:10.1016/j.theochem.2008.11.023
The Ni bis-dithiolene complexes with D2h symmetry were predicted to be stable at B3LYP/6-311++G(d) level. The analyses of nature bond orbital and nucleus-independent chemical shift (NICS) at B3LYP/6-31G(d) and GIAO-B3LYP/6-31G(d) level revealed the aromatic character of the Ni bis-dithiolene complexes. The total isotropic NICS (NICSiso) at the ring center [NICS(0)iso] has main contribution from the molecular orbitals (MOs) within the molecular plane according to the analysis of canonical MO (CMO) contributions to NICS. The π MOs have large contribution to the NICSiso at 1 Å above the ring center [NICS(1)iso]. Both analyses of CMO and nature local MO (NLMO) predict that the Ni–S σ bonds weaken the aromaticity of the Ni(S2C2H2) and Ni(bdt)2 complexes. The three d atomic orbitals with lone pair electrons of the Ni atom and the delocalized π bond among S–C–C–S have large contribution to the NICS(0)iso and NICS(1)iso in Ni(S2C2H2) and Ni(bdt)2 according to the analyses of NLMO. The C–C π bond has large contribution to the NICS(n)iso (n = 0 or 1) in Ni(S2C2H2)2, while the delocalized S–C π bond has large contribution to the NICS(n)iso (n = 0 or 1) in Ni(bdt)2.
Co-reporter:Xi Mao Li, Wei Quan Tian, Xu-Ri Huang, Chia-Chung Sun, Lei Jiang
Journal of Molecular Structure: THEOCHEM 2009 Volume 901(1–3) pp:103-109
Publication Date(Web):15 May 2009
DOI:10.1016/j.theochem.2009.01.019
Novel Pt-doped armchair (5, 5) single-walled BN nanotubes (BNNTs) have been studied within density functional theory (DFT). The Pt atom protrudes to the exterior of the sidewall and favors attack from an approaching molecule. The smaller energy gap for the Pt-doped BNNTs implies that their conductivity is higher than that of the pristine BNNT. The DFT predictions suggest a strong affinity of the Pt atom in BNNT towards hydrogen molecules. The binding energies of H2 with Pt-doped BNNTs are in the optimal range for hydrogen storage. Up to two H2 can be partially dissociated with weak chemisorption, which improves the hydrogen storage capacity.
Co-reporter:Xi Mao Li;Wei Quan Tian;Xu Ri Huang;Chia Chung Sun
Journal of Nanoparticle Research 2009 Volume 11( Issue 2) pp:395-403
Publication Date(Web):2009 February
DOI:10.1007/s11051-008-9388-x
A systematic study of armchair boron nitride nanotubes (BNNTs) with defects has been carried out within density functional theory. The effect brought by the defects is localized. The defect sites have major contribution to the frontier molecular orbital and change the conductivity of the BNNTs. The defect sites are reactive centers. The substitution of boron with carbon enhances the field emission of the tubes. Doping or vacancy defect creates active center on nanotubes, thus broadening the applications of nanotubes in chemistry and material sciences through functionalization.
Co-reporter:De-Li Chen Dr.;Wei Quan Tian Dr.;Ji-Kang Feng ;Chia-Chung Sun
ChemPhysChem 2008 Volume 9( Issue 3) pp:454-461
Publication Date(Web):
DOI:10.1002/cphc.200700616
Abstract
The complete set of 6332 classical isomers of the fullerene C68 as well as several non-classical isomers is investigated by PM3, and the data for some of the more stable isomers are refined by the DFT-based methods HCTH and B3LYP. C2:0112 possesses the lowest energy of all the neutral isomers and it prevails in a wide range of temperatures. Among the fullerene ions modeled, C682−, C684− and C686−, the isomers C682−(Cs:0064), C684−(C2v:0008), and C686−(D3:0009) respectively, are predicted to be the most stable. This reveals that the pentagon adjacency penalty rule (PAPR) does not necessarily apply to the charged fullerene cages. The vertical electron affinities of the neutral Cs:0064, C2v:0008, and D3:0009 isomers are 3.41, 3.29, and 3.10 eV, respectively, suggesting that they are good electron acceptors. The predicted complexation energy, that is, the adiabatic binding energy between the cage and encapsulated cluster, of Sc2C2@C68(C2v:0008) is −6.95 eV, thus greatly releasing the strain of its parent fullerene (C2v:0008). Essentially, C68 fullerene isomers are charge-stabilized. Thus, inducing charge facilitates the isolation of the different isomers. Further investigations show that the steric effect of the encaged cluster should also be an important factor to stabilize the C68 fullerenes effectively.
Co-reporter:De-Li Chen Dr.;Wei Quan Tian Dr.;Ji-Kang Feng ;Chia-Chung Sun
ChemPhysChem 2007 Volume 8(Issue 16) pp:2386-2390
Publication Date(Web):9 OCT 2007
DOI:10.1002/cphc.200700405
Stimulated by the recent observation of the first C56Cl10 chlorofullerene (Science, 2004, 304, 699), we performed a systematic density functional study of the structures and properties of C56Cl10 and related compounds. The fullerene derivatives C56Cl8 and C56Cl10 based on the parent fullerene C56(C2v:011), rather than those from the most stable C56 isomer with D2 symmetry, are predicted to possess the lowest energies, and they are highly aromatic. Further investigations show that the heats of formation of the C56Cl8 and C56Cl10 fullerene derivatives are highly exothermic, that is, −48.59 and −48.89 kcal mol−1 per Cl2 (approaching that of C50Cl10), suggesting that adding eight (or ten) Cl atoms releases much of the strain of pure C56(C2v:011) fullerene and leads to highly stable derivatives. In addition, C56Cl8 and C56Cl10 possess large vertical electron affinities, especially for C56Cl8 with value of 3.20 eV, which is even larger than that (3.04 eV) of C50Cl10, indicating that they are potential good electron acceptors with possible photonic/photovoltaic applications. Finally, the 13C NMR chemical shifts and infrared spectra of C56Cl8 and C56Cl10 are simulated to facilitate future experimental identification.
Co-reporter:De-Li Chen Dr.;Wei Quan Tian Dr.;Ji-Kang Feng ;Chia-Chung Sun
ChemPhysChem 2007 Volume 8(Issue 7) pp:1029-1036
Publication Date(Web):12 MAR 2007
DOI:10.1002/cphc.200600785
The 1205 classical isomers of fullerene C58, as well as one quasi-fullerene C58 isomer with a heptagonal ring (labeled as Cs:hept) have been investigated by the quantum chemical methods PM3, HCTH/3-21G, and B3LYP/6-31G(d). Isomer C3v:0001, which has the lowest number of adjacent pentagons, is predicted to be the most stable isomer, but the quasi-fullerene isomer Cs:hept is only 2.50 kcal mol−1 higher in energy. Systematic investigations of the electronic properties of C3v:0001 and Cs:hept find that the C3v:0001 isomer has high vertical electron affinity (3.19 eV). The nucleus-independent chemical shifts (NICS) value at the center of Cs:hept (−5.1 ppm) is more negative than that of C60 (−2.8 ppm). The NICS value at the center of the heptagonal ring in Cs:hept (−2.5 ppm) indicates weakly aromatic character. In contrast, the C586− and C588− ions of the C3v:0001 and Cs:hept geometries possess large aromatic character, with NICS values between −14.0 and −26.2 ppm. To clarify the thermodynamic stabilities of C58 isomers at different temperatures, the entropy contributions are taken into account on the basis of the Gibbs energy at the B3LYP/6-31G(d) level. The C3v:0001 isomer prevails in a wide range of temperatures, and the Cs:hept isomer is also an important component around 2800 K. The IR spectra of C58 isomers are simulated to facilitate experimental identification of different isomers. In addition, the electronic spectra and the second-order hyperpolarizabilities are predicted by ZINDO and the sum-over-states model. The static second-order hyperpolarizability of the C3v:0001 isomer is 96.5 % larger than that of C60, and its second-order hyperpolarizabilities at external field frequencies are at least nine times larger than those of C60.
Co-reporter:Wei-Qi Li, Wei Quan Tian, Ji-Kang Feng, Yan-Hong Cui, Zi-Zhong Liu
Journal of Molecular Structure: THEOCHEM 2007 Volume 823(1–3) pp:1-5
Publication Date(Web):1 December 2007
DOI:10.1016/j.theochem.2007.08.012
The phosphorus analogues (phosphanyl ketones) of pyridones are shown by theory to exhibit qualitatively different structures. Energy minimum of meta-phosphanyl ketone is planar while the planar conformations of the ortho- and para-isomers are transition state. Analysis of the electron density using the electron localization function (ELF) rationalizes the structural differences. In these molecules, there are competitive effects on geometry due to the octet rule, electron delocalization, and pyramidality of the tri-coordinated nitrogen or phosphorus. A delicate balance determines the molecular conformations.
Co-reporter:Yan-Hong Cui, Wei Quan Tian, Ji-Kang Feng, Zi-Zhong Liu, Wei-Qi Li
Journal of Molecular Structure: THEOCHEM 2007 Volume 810(1–3) pp:65-72
Publication Date(Web):25 May 2007
DOI:10.1016/j.theochem.2007.02.005
Some η5-cyclopentadienyl cobalt dithiolene complexes CpCoS2C2R2 have been optimized at B3LYP/6-311++G(d) level. The optimized geometries agree well with experiment. The analyses of nature bond orbital and nucleus-independent chemical shift (NICS) at B3LYP/6-311++G(d) and GIAO-B3LYP/6-311++G(d) levels reveal the aromatic character of the η5-cyclopentadienyl cobalt dithiolene complexes. However, their aromaticity is weaker than that of the isolated CoS2C2+1. There are two reasons for the change of heterocyclic aromaticity of the metal dithiolene in the η5-cyclopentadienyl cobalt dithiolene complexes with respect to that of the isolated CoS2C2+1. The better equalization of bond lengths in the isolated cation CoS2C2+1 is the first reason. The other reason is that the contribution to the NICS from the metallic cobalt atom is much larger in the isolated cation CoS2C2+1. The planar character of cyclopentadienyl is destroyed slightly in the complexes. At the same time, the size of cyclopentadienyl (Cp) becomes bigger than the isolated Cp−1 and this is caused by the cobalt atom in the pentagon. The π-electron delocalization causes stronger aromaticity of the Cp in the complexes than that of the isolated Cp−1.
