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Chen X.,Chongqing Normal University | Chen X.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | And 2 more authors.
Jisuan Wuli/Chinese Journal of Computational Physics | Year: 2017

With first-principles plane-wave ultrasoft pseudopotential method based on density functional theory (DFT), we studied acceptor level characreristics of anatase titanium dioxide doped and co-doped with 3d metal impurities Cu and non-metallic impurities C, N and F. It shows that Cu-N co-doping system and Cu, N single-doped system are better for visible light. Cu-N co-doping system, compared with Cu, N single-doped system, has a smaller band gap and greater density distribution on shallow acceptor level. It also shows that Cu-N co-doping system has highest absorption and reflectivity. Therefore, this system is the best for visible light. Cu and N acceptor level cooperative action results in the best visible light effect. © 2017, Editorial Board of Chinese Journal of Computational. All right reserved.


Li Y.,Chongqing University | Cai C.,Chongqing University | Zhao C.,Chongqing University | Gu Y.,Chongqing University | Gu Y.,Chongqing Key Laboratory on Optoelectronic Functional Materials
Modern Physics Letters B | Year: 2016

In virtue of the particle swarm optimization (PSO) algorithm, the global minimum candidate structures with the lowest energy for (Formula presented.) clusters were obtained by first-principles structural searches. The geometric structures and spin configurations of three cationic (Formula presented.) clusters have been identified for the first time by comparing the experimental IR spectra with the calculated results from density functional theory by using different exchange-correlation functionals. It is found that the lowest energy structures of these clusters are of a shape of hat, boat and tower, respectively, with a ferrimagnetic arrangement of spins, and M06L functional is more suitable for (Formula presented.) clusters than other ones. © 2016 World Scientific Publishing Company


Zhu H.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Yue Y.,Chongqing Key Laboratory on Optoelectronic Functional Materials
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2014

The change is optical properties and the extention of the application in the field of photocatalysis and photoelectric conversion of the metal and nonmetal-co-doped TiO2 are heatedly studied in recent years. The properties of band structure, density of states, optical properties and defect formation energy of rutile TiO2 super-cell with metallic and nonmetallic impurity co-doped with N-Ru, N-Rh and N-Pd are calculated by plane wave pseudopotential method based on the density functional theory. The results show that rutile TiO2 co-doped with N, N-Ru, N-Rh and N-Pd improve the visible light absorption and utilization efficiency. The defect formation energies decrease in the order of N-Pd, N-Rh and N-Ru, which shows that N-Ru is the most easily doped into TiO2 lattice in co-doped condition. TiO2 co-doped with N-Rh greatly improves absorptivity and reflectivity and achieves the best effect in the range of visible light wavelength.


Zhang J.,Chongqing Normal University | Zhang J.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | And 4 more authors.
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2015

TiO2, a kind of inorganic metal oxide semiconductor material, has been widely utilized. It is becoming a research hotspot to improve photocatalytic activity and photoelectric conversion property of TiO2 through incorporation of impurities. The electronic structure and optical properties of N doped, Cu doped and N-Cu co-doped rutile TiO2 are studied by using plane wave pseudopotential method of first-principles based on density functional theory. The results show that with N and Cu co-doped TiO2, new impurity energy levels would be formed in band gap of TiO2 due to the synergistic effect of 2p electrons of N and 3d electrons of Cu. Among them, one of impurity levels is in steady-state, the another level is in metastable state. It is favorable for decreasing the transition energy of electron and effective separation of photoproduced electrons-hole pairs, which largely improve the photocatalytic activity of TiO2. The curve of optical absorption coefficient of N-Cu co-doped TiO2 has larger red shift in the visible region than that of N doped TiO2 and Cu doped TiO2, and the reflectivity of N-Cu co-doped TiO2 also increases. ©, 2015, Science Press. All right reserved.


Zhu H.,Chongqing Normal University | Zhu H.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2015

Using the first-principles plane-wave ultrasoft pseudopotential method based on density functional theory (DFT) system, the study on titanium dioxide surface adsorption hydrogen halide gas (HX, X=F, Cl, Br) and oxygen vacancy oxidation characteristics is carried out. The calculation results show that: 1) The surface containing oxygen vacancy adsorbed hydrogen halide gas easier, whose adsorption method is chemical adsorption, among them, HF and HCl reduced by surface oxygen vacancy while HBr oxidized by surface oxygen vacancy, and the stable level of adsorption is HF>HBr>HCl; 2) adsorption hydrogen halide gas molecules can improve optical properties including dielectric constant, absorption coefficient and reflectivity of the TiO2 (110) surface, and the order of improvement ability is HF>HBr>HCl. ©, 2015, Science Press. All right reserved.


Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Yue Y.-X.,Chongqing Normal University | Yue Y.-X.,Chongqing Key Laboratory on Optoelectronic Functional Materials | And 4 more authors.
Chinese Physics B | Year: 2014

In this paper, the stable structure and the electronic and optical properties of nitric oxide (NO) adsorption on the anatase TiO2 (101) surface are studied using the plane-wave ultrasoft pseudopotential method, which is based on the density functional theory. NO adsorption on the surface is weak when the outermost layer terminates on twofold coordinated oxygen atoms, but it is remarkably enhanced on the surface containing O vacancy defects. The higher the concentration of oxygen vacancy defects, the stronger the adsorption is. The adsorption energies are 3.4528 eV (N end adsorption), 2.6770 eV (O end adsorption), and 4.1437 eV (horizontal adsorption). The adsorption process is exothermic, resulting in a more stable adsorption structure. Furthermore, O vacancy defects on the TiO2 (101) surface significantly contribute to the absorption of visible light in a relatively low-energy region. A new absorption peak in the low-energy region, corresponding to an energy of 0.9 eV, is observed. However, the TiO2 (101) surface structure exhibits weak absorption in the low-energy region of visible light after NO adsorption. © 2014 Chinese Physical Society and IOP Publishing Ltd.


Tian Y.,Chongqing Normal University | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Ding S.,Chongqing Normal University | And 3 more authors.
Guangxue Xuebao/Acta Optica Sinica | Year: 2013

Recently, through nonmetallic impurity doping rutile TiO2 to change its optical properties and expand the application in the fields of photocatalysis and photoelectric conversion is a hot research topic. The electronic properties and optical properties of rutile TiO2 super cell with nonmetallic impurity doped (including C, N, S, C-N, C-S, N-S) are calculated by plane wave pseudopotential method based on the density functional theory, such as the band structure, density of states, dielectric constant, absorption spectroscopy and reflection spectroscopy, etc. Nonmetallic elements doping makes TiO2 band gap decrease, and the absorption spectrum and reflection spectra exhibit red shift. To a certain extent, nonmetallic impurity doping improves the TiO2 utilization of visible light, but visible light utilization rate of co-doped TiO2 is higher than that of single-doped TiO2. The research results show that in the visible light high energy area from 400 nm to 575 nm, C-doped rutile TiO2 performs much better than others in absorptivity and reflectivity. In the visible light low energy area from 575 nm to 760 nm, absorptivity and reflectivity of N-doped rutile TiO2 are much better than others. Therefore, the visible light utilization in C-N co-doped TiO2 is better than those of other nonmetallic doped systems.


Zhu H.-Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Zhu H.-Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University
Wuli Xuebao/Acta Physica Sinica | Year: 2014

Using the optical gas sensing materials to adsorb gases can cause the changes of the optical properties of materials. This method can be used to measure the gas composition and is a hot topic of current research in the field of gas sensitive sensors. This paper studies the micro-characteristics of rutile TiO2 (110) surface adsorption of CO molecules. By using the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory (DFT), the adsorption energy, electron density of states, optical properties and charge density of the surface are calculated. Results show that the TiO2 (110) surface terminating in two coordinated O atoms is the most stable surface, and the structure with C-terminal of CO molecules adsorbed on the surface is the most stable. The higher the oxygen vacancy concentration, the more helpful it is to the adsorption of surface CO molecules. This process is exothermic. When the oxygen vacancy concentration is 33%, the adsorption energy can reach 1.319 eV. After adsorption, the structure of the surface tends to be more stable. Oxygen vacancy oxidizing the CO molecule is the essence of the adsorption process, and the charge of a CO molecule is transferred to the material surface. The CO molecules adsorbed on TiO2 (110) surface containing oxygen vacancies can improve its optical properties in visible light range; moreover, the higher the concentration of oxygen vacancy, the more obvious the improvement of absorption, reflection ability and optical gas sensing performance. © 2014 Chinese Physical Society.


Zhu H.,Chongqing Normal University | Zhu H.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials
Guangxue Xuebao/Acta Optica Sinica | Year: 2014

The study on characteristics of optical gas sensing materials after gas adsorption is a hot issue. The microscopic mechanism and optical characteristics of rutile titanium dioxide (110) surface adsorption NH3 molecules are studied. The results show that NH3 molecules are easy to be adsorbed by rutile titanium dioxide (110) surface containing oxygen vacancies. The higher of oxygen vacancy concentration, the more stability of NH3 adsorption, and the main way of surface adsorption NH3 molecule is negative charge center down. When oxygen vacancy concentration reached 33%, adsorption energy is 1.7313 eV. The adsorption of NH3 is chemical adsorption, and the H atom of NH3 is reduced and N atom is oxidized. In visible light range from 1.5 eV to 3.1 eV, the higher concentration of oxygen vacancy, the more obvious improvement of absorption, reflection ability and optical gas sensing performance.


Yue Y.-X.,Chongqing Normal University | Yue Y.-X.,Chongqing Key Laboratory on Optoelectronic Functional Materials | Feng Q.,Chongqing Normal University | Feng Q.,Chongqing Key Laboratory on Optoelectronic Functional Materials | And 2 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2013

Recently, non-metallic impurities doped TiO2 semiconductor to improve photocatalytic properties of visible light region was a research focus, but not many related defect formation energy research. In this paper, the defect formation energy and the electronic properties of anatase TiO2 was studied by plane wave pseudopotential method based on the density functional theory. After the three elements doped into TiO2, the order of the defect formation energy was C>N>F. The results show that F was most easily doped into the titanium dioxide lattice, but the change of band gap was very small. So F-doped was not as good as N-doped and C-doped in response effect of visible light. In view of the above two reasons, N was the best of the three dopants in improving visible light response.

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