Co-reporter:Shu-Juan Lin, Jing Cheng, Chang-Fu Zhang, Bin Wang, Yong-Fan Zhang and Xin Huang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 17) pp:11499-11508
Publication Date(Web):30 Mar 2015
DOI:10.1039/C5CP00529A
Density functional theory (DFT) calculations are employed to investigate the reactivity of tungsten oxide clusters towards carbon monoxide. Extensive structural searches show that all the ground-state structures of (WO3)n+ (n = 1–4) contain an oxygen radical center with a lengthened W–O bond which is highly active in the oxidation of carbon monoxide. Energy profiles are calculated to determine the reaction mechanisms and evaluate the effect of cluster sizes. The monomer WO3+ has the highest reactivity among the stoichiometric clusters of different sizes (WO3)n+ (n = 1–4). The reaction mechanisms for CO with mono-nuclear stoichiometric tungsten oxide clusters with different charges (WO3−/0/+) are also studied to clarify the influence of charge states. Our calculated results show that the ability to oxidize CO gets weaker from WO3+ to WO3− as the negative charge accumulates progressively.
Co-reporter:Hong-Ling Fang, Lei Xu, Jia Li, Bin Wang, Yong-Fan Zhang and Xin Huang
RSC Advances 2015 vol. 5(Issue 93) pp:76651-76659
Publication Date(Web):04 Sep 2015
DOI:10.1039/C5RA11695C
Density functional theory (DFT) calculations are employed to investigate the full catalytic cycle of CO oxidation by N2O on yttrium oxide clusters Y2MO5 (M = Y, Al) in the gas-phase. Extensive structural searches show that both the ground-state structures of Y3O5 and Y2AlO5 contain an oxygen radical (Ot˙) which plays an important role in CO oxidation. Energy profiles are calculated to determine the reaction mechanisms. Molecular electrostatic potential maps (MEPs) and natural bond orbital (NBO) analyses are employed to rationalize the reaction mechanisms. The results indicate that the whole catalytic cycle for the reaction CO + N2O → CO2 + N2, conducted by yttrium oxide clusters Y2MO5 (M = Y, Al), is favored both thermodynamically and kinetically. Moreover, compared with the previous report on di-nuclear YAlO3+˙ and Y2O3+˙, it's obvious we can conclude that tri-nuclear Y3O5 and Y2AlO5 exhibit greatly enhanced catalytic activity toward CO/N2O couples.
Co-reporter:Lei Xu, Chan-Juan Xia, Ling-Fei Wang, Lu Xie, Bin Wang, Yong-Fan Zhang and Xin Huang
RSC Advances 2014 vol. 4(Issue 104) pp:60270-60279
Publication Date(Web):27 Oct 2014
DOI:10.1039/C4RA09202C
We report a systematic and comprehensive investigation on the electronic structures and chemical bonding of a series of tri-yttrium oxide clusters, Y3Ox−/0 (x = 0–6), using density functional theory (DFT) calculations. The generalized Koopmans' theorem was applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES) for Y3Ox− (x = 0–6) clusters. A trend of sequential oxidation is observed from Y3O− to Y3O6−. All of these clusters tend to form structures with a capped oxygen atom. For Y3Ox−/0 (x = 2–4), the O atoms prefer the bridging sites of Y3O−/0, whereas the fifth O atoms for Y3O5−/0 are bonded to the terminal sites. In particular, the ground states of Y3O6−/0 are found to be interesting species, which may be viewed as molecular models for dioxygen activation by Y3O4−/0. σ- and π-aromaticity is found in Y3− by the molecular orbital analysis and Adaptive Natural Density Partitioning (AdNDP) analysis. Molecular orbital analyses are performed to analyze the chemical bonding in the tri-yttrium oxide clusters and to elucidate their electronic and structural evolution.
Co-reporter:Wei-Li Li;Lu Xie;Tian Jian;Dr. Constantin Romanescu;Dr. Xin Huang;Dr. Lai-Sheng Wang
Angewandte Chemie 2014 Volume 126( Issue 5) pp:1312-1316
Publication Date(Web):
DOI:10.1002/ange.201309469
Abstract
It has been a long-sought goal in cluster science to discover stable atomic clusters as building blocks for cluster-assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses.1, 2 Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid-state chemistry.3 Because of its electron deficiency, boron is an interesting element with unusual polymorphism. While bulk boron is known to be dominated by the three-dimensional (3D) B12 icosahedral motifs,4 new forms of elemental boron are continuing to be discovered.5 In contrast to the 3D cages commonly found in bulk boron, in the gas phase two-dimensional (2D) boron clusters are prevalent.6–8 The unusual planar boron clusters have been suggested as potential new bulking blocks or ligands in chemistry.6a Herein we report a joint experimental and theoretical study on the [Ta2B6]− and [Ta2B6] clusters. We found that the most stable structures of both the neutral and anion are D6h bipyramidal, similar to the recently discovered MB6M structural motif in the Ti7Rh4Ir2B8 solid compound.9
Co-reporter:Wei-Li Li;Lu Xie;Tian Jian;Dr. Constantin Romanescu;Dr. Xin Huang;Dr. Lai-Sheng Wang
Angewandte Chemie International Edition 2014 Volume 53( Issue 5) pp:1288-1292
Publication Date(Web):
DOI:10.1002/anie.201309469
Abstract
It has been a long-sought goal in cluster science to discover stable atomic clusters as building blocks for cluster-assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses.1, 2 Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid-state chemistry.3 Because of its electron deficiency, boron is an interesting element with unusual polymorphism. While bulk boron is known to be dominated by the three-dimensional (3D) B12 icosahedral motifs,4 new forms of elemental boron are continuing to be discovered.5 In contrast to the 3D cages commonly found in bulk boron, in the gas phase two-dimensional (2D) boron clusters are prevalent.6–8 The unusual planar boron clusters have been suggested as potential new bulking blocks or ligands in chemistry.6a Herein we report a joint experimental and theoretical study on the [Ta2B6]− and [Ta2B6] clusters. We found that the most stable structures of both the neutral and anion are D6h bipyramidal, similar to the recently discovered MB6M structural motif in the Ti7Rh4Ir2B8 solid compound.9
Co-reporter:Qi Zhou, Wei-Chao Gong, Lu Xie, Cun-Gong Zheng, Wei Zhang, Bin Wang, Yong-Fan Zhang, Xin Huang
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2014 Volume 117() pp:651-657
Publication Date(Web):3 January 2014
DOI:10.1016/j.saa.2013.09.059
•DFT and CCSD calculations are carried out to verify the ground states for Re3On.•Generalized Koopmans’ theorem is applied to simulate the photoelectron spectra.•MO analyses are employed to study the structural evolution of Re3On clusters.Density functional theory (DFT) calculations are performed to study the structural and electronic properties of tri-rhenium oxide clusters Re3On-/0 (n = 1–6). Generalized Koopmans’ theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES). Theoretical calculations at the B3LYP level are carried out to search for the global minima for both the anions and the neutrals. For the anions, the first two O atoms prefer the same corner position of a Re3 triangle. Whereas, Re3O3- possesses a C2v symmetry with one bridging and two terminal O atoms. The next three O atoms (n = 4–6) are adding sequentially on the basis of Re3O3- motif, i.e., adding one terminal O atom for Re3O4-, one terminal and one bridging O atoms for Re3O5-, and one terminal and two bridging O atoms for Re3O6-, respectively. Their corresponding neutral species are similar to the anions in geometry except Re3O4 and Re3O5. Molecular orbital analyses are employed to investigate the chemical bonding and structural evolution in these tri-rhenium oxide clusters.
Co-reporter:Ling-Fei Wang, Lu Xie, Hong-Ling Fang, Yun-Fei Li, Xiao-Bin Zhang, Bin Wang, Yong-Fan Zhang, Xin Huang
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2014 Volume 131() pp:446-454
Publication Date(Web):15 October 2014
DOI:10.1016/j.saa.2014.04.094
•DFT calculations are applied to verify the ground states of V6On−/0 clusters.•The V6On−/0 clusters appear to prefer the polyhedral cage structures.•Generalized Koopmans’ theorem is applied to simulate the photoelectron spectra.•Spin density analyses show that the spin densities of V6On− favor the V3+ site.Density functional theory (DFT) calculations are carried out to investigate the structural and electronic properties of a series of hexanuclear vanadium oxide clusters V6On−/0 (n = 12–15). Generalized Koopmans’ theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES) for V6On− (n = 12–15) clusters. Extensive DFT calculations are performed in search of the lowest-energy structures for both the anions and neutrals. All of these clusters appear to prefer the polyhedral cage structures, in contrast to the planar star-like structures observed in prior model surface studies for the V6O12 cluster. Molecular orbitals are performed to analyze the chemical bonding in the hexanuclear vanadium oxide clusters and provide insights into the sequential oxidation of V6On− (n = 12–15) clusters. The V6On− (n = 12–15) clusters possess well-defined V5+ and V3+ sites, and may serve as molecular models for surface defects. Electron spin density analyses show that the unpaired electrons in V6On− (n = 12–14) clusters are primarily localized on the V3+ sites rather than on the V5+ sites. The difference gas phase versus model surface structures of V6O12 hints the critical roles of cluster–substrate interactions in stabilizing the planar V6O12 cluster on model surfaces.Graphical abstract
Co-reporter:Hua-Jin Zhai, Wen-Jie Chen, Shu-Juan Lin, Xin Huang, and Lai-Sheng Wang
The Journal of Physical Chemistry A 2013 Volume 117(Issue 6) pp:1042-1052
Publication Date(Web):June 6, 2012
DOI:10.1021/jp302822p
The electronic and structural properties of monohafnium oxide clusters, HfOn– and HfOn (n = 1–6), are investigated using anion photoelectron spectroscopy and density-functional theory at the B3LYP level. The observed ground-state adiabatic detachment energy is low for HfO– (0.5 ± 0.1 eV) and HfO2– (2.125 ± 0.010 eV), roughly constant for HfO3– (3.6 ± 0.1 eV), HfO4– (3.67 ± 0.05 eV), and HfO5– (3.9 ± 0.1 eV), and substantially higher for HfO6– (4.9 ± 0.1 eV). Activated oxygen species, such as radical, superoxide, peroxide, diradical, and triradical, are identified in the HfOn– and HfOn clusters. The Hf center is shown to be flexible to accommodate the oxygen species. The sum of formal Hf–O bond orders around the Hf center is equal to four for all of the neutral clusters studied, and five for all of the anions. The O-rich HfOn– and HfOn (n = 3–6) clusters provide well-defined molecular models to understand O2 adsorption and activation on an Hf center.
Co-reporter:Shu-Juan Lin, Xian-Hui Zhang, Lei Xu, Bin Wang, Yong-Fan Zhang, and Xin Huang
The Journal of Physical Chemistry A 2013 Volume 117(Issue 14) pp:3093-3099
Publication Date(Web):March 17, 2013
DOI:10.1021/jp400673s
Density functional theory (DFT) calculations are employed to investigate the structural and electronic properties of bare tritungsten clusters (W3, W3–, W32–) and tritungsten oxide clusters W3Ox–/0 (x = 1, 2). Generalized Koopmans’ theorem is applied to predict the vertical detachment energies and simulate the photoelectron spectra (PES) for W3Ox– (x = 0–2) clusters. Extensive DFT calculations are performed in search of the lowest energy structures for both the anions and the neutrals. The bare tritungsten clusters are predicted to be triangular structures with D3h (3A1′), C2v (2A1) and D3h (1A1′) symmetry for W3, W3– and W32–, respectively. For W3O– and W3O clusters, the oxygen atom occupies the terminal site, while the next added oxygen atom is found to be a bridging one in both W3O2– and W3O2 clusters. Molecular orbital analyses are carried out to elucidate the chemical bonding of these clusters and provide insights into the sequential oxidation from W3– to W3O2–. Partial σ- and δ-aromaticity are revealed in the neutral W3 (D3h, 3A1′), while the anion W32– (D3h, 1A1′) possesses only δ-aromaticity.
Co-reporter:Wen-Jie Chen, Chang-Fu Zhang, Xian-Hui Zhang, Yong-Fan Zhang, Xin Huang
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2013 Volume 109() pp:125-132
Publication Date(Web):15 May 2013
DOI:10.1016/j.saa.2013.02.011
Density functional theory (DFT) and coupled cluster theory (CCSD(T)) calculations are carried out to investigate the electronic and structural properties of a series of bimetallic oxide clusters MW2O9-/0 (M = V, Nb, Ta). Generalized Koopmans’ theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES). Theoretical calculations at the B3LYP level yield singlet and doublet ground states for the bimetallic anionic and neutral clusters, respectively. All the clusters present the six-membered ring structures with different symmetries, except that the TaW2O9- cluster shows a chained style with a penta-coordinated tantalum atom. Spin density analyses reveal oxygen radical species in all neutral clusters, consistent with their structural characteristics. Moreover, additional calculations are performed to study the oxidation reaction of CO molecule with the W3O9+ cation and the isoelectronic VW2O9 cluster, and results indicate that the introduction of vanadium at tungsten site can efficiently improve the oxidation reactivity.Graphical abstractHighlights► The TaW2O9- cluster shows a chained style with a penta-coordinated tantalum atom. ► Generalized Koopmans’ theorem is applied to simulate the photoelectron spectra. ► We report some interesting radical species with high electron affinities. ► Introduction of V atom at W site can efficiently improve the oxidative reactivity.
Co-reporter:Hua Jin, Jia Zhu, Wenjie Chen, Zhenxing Fang, Yi Li, Yongfan Zhang, Xin Huang, Kaining Ding, Lixin Ning, and Wenkai Chen
The Journal of Physical Chemistry C 2012 Volume 116(Issue 8) pp:5067-5075
Publication Date(Web):February 8, 2012
DOI:10.1021/jp210171f
The γ-WO3(001) surfaces doped by a series of group VB elements have been investigated by means of first-principles density functional theory (DFT) calculations combined with a slab model. Our results show that the doping of VB element is preferential under O-rich growth conditions and that the replacement of tungsten by Ta atom is energetically favorable among three group VB elements. The introduction of a group VB atom into the surface results in the downward shift of the Fermi level, and in most cases, the 2p states derived from the in-plane oxygen atom are still the dominate components at the Fermi level as before doping. However, the substitution of Ta dopant for 6-fold-coordinated tungsten atom (W6f) at the top layer is a special case in which the 2p states of the top terminal oxygen atom just above Ta become the primary compositions at the Fermi level. Only in this model, the spin densities are mainly located on the terminal oxygen atoms near the Ta site, and the oxygen radical center observed in the gas-phase W3O9+ cluster is reproduced. Therefore, the formation of radical oxygen center in the condensed phase depends on not only the substituent site but also the type of the dopant. Moreover, additional calculations are performed to study the oxidation reaction of CO molecule on the above Ta doped surface, and results indicate that the energy barrier for CO oxidization is obviously reduced compared to the undoped one, which implies that the introduction of Ta at W6f site can efficiently improve the oxidation reactivity of the WO3(001) surface.
Co-reporter:Hua-Jin Zhai ; Xian-Hui Zhang ; Wen-Jie Chen ; Xin Huang ;Lai-Sheng Wang
Journal of the American Chemical Society 2011 Volume 133(Issue 9) pp:3085-3094
Publication Date(Web):February 9, 2011
DOI:10.1021/ja110061v
We investigated the structures and bonding of two series of early transition-metal oxide clusters, M2On− and M2On (M = Nb, Ta; n = 5−7) using photoelectron spectroscopy (PES) and density-functional theory (DFT). The stoichiometric M2O5 clusters are found to be closed shell with large HOMO−LUMO gaps, and their electron affinities (EAs) are measured to be 3.33 and 3.71 eV for M = Nb and Ta, respectively; whereas EAs for the oxygen-rich clusters are found to be much higher: 5.35, 5.25, 5.28, and 5.15 eV for Nb2O6, Nb2O7, Ta2O6, and Ta2O7, respectively. Structural searches at the B3LYP level yield triplet and doublet ground states for the oxygen-rich neutral and anionic clusters, respectively. Spin density analyses reveal oxygen radical, diradical, and superoxide characters in the oxygen-rich clusters. The M2O7− and M2O7 clusters, which can be viewed to be formed by M2O5−/0 + O2, are utilized as molecular models to understand dioxygen activation on M2O5− and M2O5 clusters. The O2 adsorption energies on the stoichiometric M2O5 neutrals are shown to be surprisingly high (1.3−1.9 eV), suggesting strong capabilities to activate O2 by structural defects in Nb and Ta oxides. The PES data also provides valuable benchmarks for various density functionals (B3LYP, BP86, and PW91) for the Nb and Ta oxides.
Co-reporter:Wen-Jie Chen, Hua-Jin Zhai, Xin Huang, Lai-Sheng Wang
Chemical Physics Letters 2011 Volume 512(1–3) pp:49-53
Publication Date(Web):16 August 2011
DOI:10.1016/j.cplett.2011.07.018
Co-reporter:Jia Zhu, Hua Jin, Lili Zang, Yi Li, Yongfan Zhang, Kaining Ding, Xin Huang, Lixin Ning, and Wenkai Chen
The Journal of Physical Chemistry C 2011 Volume 115(Issue 31) pp:15335-15344
Publication Date(Web):July 5, 2011
DOI:10.1021/jp201094a
A series of nonstoichiometric tritungsten oxide clusters W3On (n = 7, 8, 10) deposited on the TiO2(110) surface have been investigated by using first-principles DFT calculations. Various possible configurations have been considered for each W3On/TiO2(110) system, based upon ab initio molecular dynamics simulations and thermodynamical analyses. After deposition of the W3On cluster, the position of the Fermi level is sensitive to the stoichiometry of the cluster. This is due to the obvious charge transfer occurring from the oxygen-deficient W3On cluster (n < 9) to the TiO2(110) surface, whereas the direction of charge transfer is reversed for the deposition of the oxygen-enriched W3On cluster (n > 9). Our results clearly indicate that the deposition of clusters with different stoichiometric compositions offers an opportunity to control the properties of the support, including the conductivity, the surface work function, and the catalytic performance over a sufficient range. In addition, our results show that the relative stability of nonstoichiometric tritungsten oxide clusters in the gas phase is not preserved after landing on the TiO2(110) surface. Therefore, from a thermodynamical point of view, it may provide a possible way to stabilize the unstable clusters in the gas phase by choosing a suitable support.
Co-reporter:Xu-Min Zhao;Wen-Jie Chen;Xian-Hui Zhang;Wen-Bin Liu
Journal of Cluster Science 2011 Volume 22( Issue 3) pp:
Publication Date(Web):2011 September
DOI:10.1007/s10876-011-0381-7
Density functional theory (DFT) calculations are carried out to investigate the electronic and structural properties of a series of bimetallic oxygen-rich clusters, MM′O7− (M, M′ = V, Nb, Ta). Generalized Koopmans’ theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES). Theoretical calculations at the B3LYP level yield dibridged structures with doublet state (Cs, 2A′′) as ground states for the anionic clusters. Intriguingly, an O2 unit is found to be bonded to the metal atom which is inclined to donate electrons in the MM′O7− (M, M′ = V, Nb, Ta) species. The extremely high binding energies, above 5.50 eV, are due to oxygen 2p-based orbitals and suggest that these clusters are strong oxidizers. Chemical bonding analyses reveal superoxide in the oxygen-rich clusters, in excellent consistence with their structural characteristics.
Co-reporter:Hua Jin;Jia Zhu;Jianming Hu;Yi Li;Yongfan Zhang
Theoretical Chemistry Accounts 2011 Volume 130( Issue 1) pp:
Publication Date(Web):2011/09/01
DOI:10.1007/s00214-011-0996-7
Geometries and electronic structures of WO3(001) surface and a series of stoichiometric (WO3)n clusters (n = 1–6) have been systematically investigated using first-principles density functional calculations. Six possible reconstructured models of WO3(001) surface with cubic phase are explored, and the most stable configuration is the \( (\sqrt 2 \times \sqrt 2 )R45^{\circ} \) surface. The main feature of WO3(001) surface is that the top of valence band is dominated by the 2p states of the bridging oxygen atom, rather than the top terminal oxygen. By comparing the geometrical parameters, from the structural point of view, the W3O9 cluster can be used as the smallest molecular prototype of the WO3 surface. However, in terms of the electronic structure, only until W6O18, the cluster begins to appear the electronic feature of the WO3(001) surface. This may be due to the reason that the W6O18 cluster and the top layer of WO3(001) surface show similar “stoichiometry” if we treat two kinds of oxygen atoms as different “elements”. In addition, for the chemical reactivity, using BH3 as a probe molecule, the W6O18 cluster also bears general resemblance to the WO3(001) surface, and the bridging oxygen atoms in two systems are the preferred sites for the nucleophilic reaction. Therefore, our results indicate that the W6O18 cluster with a spherical buckyball structure can be viewed as the smallest molecular model to understand the properties such as catalytic activity of WO3(001) surface.
Co-reporter:Wen-Jie Chen, Hua-Jin Zhai, Yong-Fan Zhang, Xin Huang and Lai-Sheng Wang
The Journal of Physical Chemistry A 2010 Volume 114(Issue 19) pp:5958-5966
Publication Date(Web):April 29, 2010
DOI:10.1021/jp102439v
The electronic and structural properties of a series of triniobium oxide clusters, Nb3On− and Nb3On (n = 3−8), are investigated using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. PES spectra are obtained for Nb3On− (n = 3−8) at various photon energies and are used to compare with the DFT calculations. A trend of sequential oxidation is observed as a function of O content until Nb3O8−, reaching the highest oxidation state of Nb. DFT calculations are performed to search for the lowest energy structures for both the anionic and neutral clusters. For Nb3O3−, the three O atoms are shown to prefer the bridging sites of a triangular Nb3, leading to two nearly degenerate cyclic structures of Cs symmetry. The next three O atoms from n = 4−6 each occupy a terminal site directly bonded to Nb, resulting in a symmetric Nb3O6− with C3v symmetry and a low-lying isomer of Cs symmetry. The seventh O atom is bonded to two Nb atoms forming a double bridge, whereas the eighth O atom is bonded to a terminal site so that in Nb3O8− each Nb atom reaches its maximum oxidation state of +5. The structures and electronic states for the triniobium oxide clusters are significantly different from the corresponding tritantalum oxide clusters, in particular, for Nb3O3−, Nb3O5−, and Nb3O7−. Molecular orbital analyses are performed to elucidate the chemical bonding and the electronic and structural evolution in these triniobium oxide clusters.
Co-reporter:Bin Wang, Wen-Jie Chen, Bo-Cun Zhao, Yong-Fan Zhang and Xin Huang
The Journal of Physical Chemistry A 2010 Volume 114(Issue 4) pp:1964-1972
Publication Date(Web):December 31, 2009
DOI:10.1021/jp909676s
Density functional theory (DFT) calculations are carried out to investigate the electronic and structural properties of a series of tetratungsten oxide clusters, W4On−/0 (n = 10−13). Generalized Koopmans’ theorem is applied to predict the vertical detachment energies and simulate the photoelectron spectra (PES). A large energy gap (∼2.9 eV) is observed for the stoichiometric W4O12 cluster, which reaches the bulk value. The calculations suggest that W4O12−/0 have the planar eight-membered ring structures, in which each tungsten atom is tetrahedrally coordinated with two bridging O atoms and two terminal O atoms. W4O10−/0 and W4O11− can be viewed as removing two and one terminal O atoms from W4O12−/0, respectively. The W4O11 neutral is an interesting species, which possesses the pentabridged structure. We show that W4O11− contains a localized W3+ site, which can readily react with O2 to form the W4O13− cluster, whereas the corresponding neutral W4O13 can be viewed as replacing a terminal oxygen in W4O12 by a peroxo O2 unit. Molecular orbital analyses are performed to analyze the chemical bonding in the tetratungsten oxide clusters and to elucidate their electronic and structural evolution.
Co-reporter:Hua-Jin Zhai, Bin Wang, Xin Huang and Lai-Sheng Wang
The Journal of Physical Chemistry A 2009 Volume 113(Issue 16) pp:3866-3875
Publication Date(Web):February 6, 2009
DOI:10.1021/jp809945n
We report a photoelectron spectroscopy and density functional theory (DFT) study on the electronic and structural properties of Nb3−, Nb3O−, Nb3O2−, and the corresponding neutrals. Well-resolved photoelectron spectra are obtained for the anion clusters at different photon energies and are compared with DFT calculations to elucidate their structures and chemical bonding. We find that Nb3− possesses a C2v (3A2) structure, and Nb3 is a scalene Cs (2A′′) triangle. Both Nb3O− and Nb3O are found to have C2v structures, in which the O atom bridges two Nb atoms in a Nb3 triangle. The ground-state of Nb3O2− is found surprisingly to be a low symmetry C1 (1A) structure, which contains a bridging and a terminal O atom. Molecular orbital analyses are carried out to understand the structures and bonding of the three clusters and provide insights into the sequential oxidation from Nb3− to Nb3O2−. The terminal Nb═O unit is common in niobia catalysts, and the Nb3O2− cluster with a Nb═O unit may be viewed as a molecular model for the catalytic sites or the initial oxidation of a Nb surface.
Co-reporter:Jia Zhu, Hua Jin, Wenjie Chen, Yi Li, Yongfan Zhang, Lixin Ning, Xin Huang, Kaining Ding and Wenkai Chen
The Journal of Physical Chemistry C 2009 Volume 113(Issue 40) pp:17509-17517
Publication Date(Web):September 15, 2009
DOI:10.1021/jp906194t
The stoichiometric tritungsten oxide cluster (W3O9) deposited on the TiO2(110) surface has been investigated using first-principles density functional theory calculations. Various possible configurations mainly derived from molecular dynamics simulations have been considered. On the basis of the comparisons of thermodynamic stability and STM images, two isoenergetic structures with chirality relationship between the geometries of W3O9 clusters can be tentatively assigned to be the most likely configurations under the experimental conditions, in which five new bonds including three Ti−O and two W−O bonds are formed at the interface. Due to the loss of three W═O groups, the low chemical reactivity of the W3O9 cluster can be expected. After deposition of W3O9, the TiO2(110) surface still retains the semiconducting character and the charge transfer occurring between the cluster and the substrate is small. The variation of surface dipole moment is sensitive to the orientation of the six-membered ring structure of W3O9. In addition, our results indicate that the properties of the TiO2(110) surface may be adjusted by deposition of nonstoichiometric tungsten oxides.
Co-reporter:Hua-Jin Zhai, Bin Wang, Xin Huang and Lai-Sheng Wang
The Journal of Physical Chemistry A 2009 Volume 113(Issue 36) pp:9804-9813
Publication Date(Web):August 14, 2009
DOI:10.1021/jp905478w
We report a combined photoelectron spectroscopy (PES) and density functional theory (DFT) study on a series of tritantalum oxide clusters, Ta3On−. Well-resolved PES spectra are obtained for Ta3On− (n = 1−8) at several detachment photon energies, yielding electronic structure information which is used for comparison with the DFT calculations. A trend of sequential oxidation is observed as a function of O content until Ta3O8−, which is a stoichiometric cluster. Extensive DFT calculations are performed in search of the lowest energy structures for both the anions and neutrals. The first three O atoms are shown to successively occupy the bridging sites in the Ta3 triangle. The next three O atoms each occupy a terminal site, with the seventh and eighth O atoms forming a double-bridge and a double-terminal, respectively. The Ta3O7− anion is found to possess a localized electron pair on a single Ta center, making it an interesting molecular model for Ta3+ surface sites. Molecular orbital analyses are performed to elucidate the chemical bonding in the Ta3On− clusters.
Co-reporter:Bin Wang, Hua-Jin Zhai, Xin Huang and Lai-Sheng Wang
The Journal of Physical Chemistry A 2008 Volume 112(Issue 43) pp:10962-10967
Publication Date(Web):October 3, 2008
DOI:10.1021/jp806166h
The electronic structure and chemical bonding in the Ta3− cluster are investigated using photoelectron spectroscopy and density functional theory calculations. Photoelectron spectra are obtained for Ta3− at four photon energies: 532, 355, 266, and 193 nm. While congested spectra are observed at high electron binding energies, several low-lying electronic transitions are well resolved and compared with the theoretical calculations. The electron affinity of Ta3 is determined to be 1.35 ± 0.03 eV. Extensive density functional calculations are performed at the B3LYP/Stuttgart +2f1g level to locate the ground-state and low-lying isomers for Ta3 and Ta3−. The ground-state for the Ta3− anion is shown to be a quintet (5A1′) with D3h symmetry, whereas two nearly isoenergetic states, C2v (4A1) and D3h (6A1′), are found to compete for the ground-state for neutral Ta3. A detailed molecular orbital analysis is performed to elucidate the chemical boding in Ta3−, which is found to possess multiple d-orbital aromaticity, commensurate with its highly symmetric D3h structure.
Co-reporter:Shu-Juan Lin, Jing Cheng, Chang-Fu Zhang, Bin Wang, Yong-Fan Zhang and Xin Huang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 17) pp:NaN11508-11508
Publication Date(Web):2015/03/30
DOI:10.1039/C5CP00529A
Density functional theory (DFT) calculations are employed to investigate the reactivity of tungsten oxide clusters towards carbon monoxide. Extensive structural searches show that all the ground-state structures of (WO3)n+ (n = 1–4) contain an oxygen radical center with a lengthened W–O bond which is highly active in the oxidation of carbon monoxide. Energy profiles are calculated to determine the reaction mechanisms and evaluate the effect of cluster sizes. The monomer WO3+ has the highest reactivity among the stoichiometric clusters of different sizes (WO3)n+ (n = 1–4). The reaction mechanisms for CO with mono-nuclear stoichiometric tungsten oxide clusters with different charges (WO3−/0/+) are also studied to clarify the influence of charge states. Our calculated results show that the ability to oxidize CO gets weaker from WO3+ to WO3− as the negative charge accumulates progressively.
