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Temperature-dependent evolution of surface charge screening and polarization at ferroelectric surfaces
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作者 LongFei Wang Yi Luo +8 位作者 JieSu Wang XiuShi Huang ZhaoMeng Gao TieYing Yang XiaoLong Li Pei Li KuiJuan Jin WeiFeng Zhang HaiZhong Guo 《中国科学:物理学、力学、天文学英文版》 SCIE EI CAS CSCD 2019年第8期117-120,共4页
The polarization and domain behavior on the surface of a ferroelectric material are significantly affected by the screening processes [1-12].Recently,there has been a notable increase in the theoretical calculations a... The polarization and domain behavior on the surface of a ferroelectric material are significantly affected by the screening processes [1-12].Recently,there has been a notable increase in the theoretical calculations and experiments investigating the dynamics of polarization and domain behaviors coexisting in phase transitions of ferroelectric materials. 展开更多
关键词 significantly AFFECTED SCREENING processes THEORETICAL calculations
Encapsulating a Ni(Ⅱ) molecular catalyst in photoactive metal-organic framework for highly efficient photoreduction of CO2
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作者 Zhi-Hao Yan Bo Ma +8 位作者 Shu-Rong Li Junxue Liu Rong Chen Ming-Hao Du Shengye Jin Gui-Lin Zhuang La-Sheng Long Xiang-Jian Kong Lan-Sun Zheng 《科学通报:英文版》 SCIE EI CSCD 2019年第14期976-985,共10页
Photocatalytic reduction of CO2 to CO is a promising strategy for reducing atmospheric CO2 levels and storing solar radiation as chemical energy.Here,we demonstrate that a molecular catalyst[NiⅡ(bpet)(H2O)2]successfu... Photocatalytic reduction of CO2 to CO is a promising strategy for reducing atmospheric CO2 levels and storing solar radiation as chemical energy.Here,we demonstrate that a molecular catalyst[NiⅡ(bpet)(H2O)2]successfully encapsulated into a highly robust and visible-light responsive metal–organic framework(Ru-UiO-67)to fabricate composite catalysts for photocatalytic CO2 reduction.The composite Ni@Ru-UiO-67 photocatalysts show efficient visible-light-driven CO2 reduction to CO with a TON of 581 and a selectivity of 99% after 20-h illumination,because of the facile electron transfer from Ru-photosensitizer to Ni(Ⅱ)active sites in Ni@Ru-UiO-67 system.The mechanistic insights into photoreduction of CO2 have been studied based on thermodynamical,electrochemical,and spectroscopic investigation,together with density functional theory(DFT)calculations.This work shows that encapsulating molecular catalyst into photoactive MOF highlights opportunities for designing efficient,stable and recyclable photocatalysts. 展开更多
关键词 METAL-ORGANIC frameworks CO2 reduction TRANSIENT ABSORPTION PHOTOCATALYSIS DFT CALCULATIONS
Effects of Various Deformation on the First Fission Barrier in Even-A N = 152 Isotones
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作者 柴清祯 赵维娟 王华磊 《理论物理通讯:英文版》 SCIE CAS CSCD 2019年第1期67-74,共8页
The first(namely, inner) fission barriers for even-A N = 152 nuclei have been studied systematically in the framework of macroscopic-microscopic model by means of potential energy surface(PES) calculations in the thre... The first(namely, inner) fission barriers for even-A N = 152 nuclei have been studied systematically in the framework of macroscopic-microscopic model by means of potential energy surface(PES) calculations in the threedimensional(β2, γ, β4) deformation space. Their collective properties, such as ground-state deformations, are compared with previous calculations and available observations, showing a consistent trend. In addition, it has been found that the microscopic shell correction energy plays an important role on surviving fission in these N = 152 deformed shell nuclei. The inclusion of non-axial symmetric degree of freedom γ will pull the fission barrier down more significantly with respect to the calculation involving in hexadecapole deformation β4. Furthermore, the calculated Woods-Saxon(WS) single particle levels indicate that the large microscopic shell correction energies due to low level densities may be responsible for such a reduction on the inner fission barrier. 展开更多
关键词 FISSION barriers potential ENERGY surface calculations GROUND-STATE deformations shell CORRECTION ENERGY single particle levels
Surface multiferroics in silicon enabled by hole-carrier doping
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作者 Xiaoyu Xuan Wanlin Guo Zhuhua Zhang 《科学通报:英文版》 SCIE EI CSCD 2019年第5期331-336,共6页
We predict a coexistence of magnetic and electric orders on clean Si(001)surfaces by first-principles calculations.Upon hole-carrier doping,the Si surfaces can be ferromagnetic,with polarized spins concentrated in an ... We predict a coexistence of magnetic and electric orders on clean Si(001)surfaces by first-principles calculations.Upon hole-carrier doping,the Si surfaces can be ferromagnetic,with polarized spins concentrated in an atom-thick space near the surface,due to an exchange splitting of localized s-like surface states on surface Si dimers.The surface magnetization can be controlled by reorienting the electric polarization of Si dimers,manifested as a transition from the magnetic antiferroelectric ground state to ferroelectric p(2×1)reconstruction that can be driven by an in-plane external electric field.The coupling between magnetic and electric orders can be further enhanced by strain silicon technology,rendering the Si surfaces as the first metal-free material displaying a multiferroic behavior. 展开更多
关键词 Si(OO1) FERROMAGNETISM Electric DIPOLE CARRIER DOPING ABINITIO calculations
Bimetallic Nickel Cobalt Sulfide as E cient Electrocatalyst for Zn–Air Battery and Water Splitting
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作者 Jingyan Zhang Xiaowan Bai +5 位作者 Tongtong Wang Wen Xiao Pinxian Xi Jinlan Wang Daqiang Gao John Wang 《纳微快报:英文版》 CAS CSCD 2019年第1期33-45,共13页
The development of e cient earth-abundant electrocatalysts for oxygen reduction, oxygen evolution, and hydrogen evolution reactions(ORR, OER, and HER) is important for future energy conversion and energy storage devic... The development of e cient earth-abundant electrocatalysts for oxygen reduction, oxygen evolution, and hydrogen evolution reactions(ORR, OER, and HER) is important for future energy conversion and energy storage devices, for which both rechargeable Zn–air batteries and water splitting have raised great expectations. Herein, we report a single-phase bimetallic nickel cobalt sulfide((Ni,Co)S2) as an e cient electrocatalyst for both OER and ORR. Owing to the synergistic combination of Ni and Co, the(Ni,Co)S2 exhibits superior electrocatalytic performance for ORR, OER, and HER in an alkaline electrolyte, and the first principle calculation results indicate that the reaction of an adsorbed O atom with a H2O molecule to form a *OOH is the potential limiting step in the OER. Importantly, it could be utilized as an advanced air electrode material in Zn–air batteries, which shows an enhanced charge–discharge performance(charging voltage of 1.71 V and discharge voltage of 1.26 V at 2 mA cm-2), large specific capacity(842 mAh gZn-1 at 5 mA cm-2), and excellent cycling stability(480 h). Interestingly, the(Ni,Co)S2-based Zn–air battery can e ciently power an electrochemical water-splitting unit with(Ni,Co)S2 serving as both the electrodes. This reveals that the prepared(Ni,Co)S2 has promising applications in future energy conversion and energy storage devices. 展开更多
关键词 (Ni Co)S2 NANOSHEET arrays DFT calculations Zn–air batteries Water SPLITTING
Electronic properties of size-dependent MoTe2/WTe2 heterostructure
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作者 刘婧 马亚强 +4 位作者 戴雅薇 陈炀 李依 唐亚楠 戴宪起 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第10期490-497,共8页
Lateral two-dimensional(2D) heterostructures have opened up unprecedented opportunities in modern electronic device and material science. In this work, electronic properties of size-dependent MoTe2/WTe2 lateral hetero... Lateral two-dimensional(2D) heterostructures have opened up unprecedented opportunities in modern electronic device and material science. In this work, electronic properties of size-dependent MoTe2/WTe2 lateral heterostructures(LHSs)are investigated through the first-principles density functional calculations. The constructed periodic multi-interfaces patterns can also be defined as superlattice structures. Consequently, the direct band gap character remains in all considered LHSs without any external modulation, while the gap size changes within little difference range with the building blocks increasing due to the perfect lattice matching. The location of the conduction band minimum(CBM) and the valence band maximum(VBM) will change from P-point to Γ-point when m plus n is a multiple of 3 for A-mn LHSs as a result of Brillouin zone folding. The bandgap located at high symmetry Γ-point is favourable to electron transition, which might be useful to optoelectronic device and could be achieved by band engineering. Type-II band alignment occurs in the MoTe2/WTe2 LHSs, for electrons and holes are separated on the opposite domains, which would reduce the recombination rate of the charge carriers and facilitate the quantum efficiency. Moreover, external biaxial strain leads to efficient bandgap engineering. MoTe2/WTe2 LHSs could serve as potential candidate materials for next-generation electronic devices. 展开更多
关键词 FIRST-PRINCIPLES CALCULATIONS ELECTRONIC structures MoTe2/WTe2 SUPERLATTICE strain effects
Negative Thermal Expansion of GaFe(CN)6 and Effect of Na Insertion by First-Principles Calculations
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作者 李蒙 李媛 +1 位作者 王春艳 孙强 《中国物理快报:英文版》 SCIE CAS CSCD 2019年第6期37-40,共4页
We study the negative thermal expansion(NTE) properties and effect of Na insertion on the NTE of the framework material GaFe(CN)6 by first-principles calculations based on density functional theory within the quasi-ha... We study the negative thermal expansion(NTE) properties and effect of Na insertion on the NTE of the framework material GaFe(CN)6 by first-principles calculations based on density functional theory within the quasi-harmonic approximation. The calculated results show that the material exhibits NTE due to the low transverse vibrational modes of the CN groups. The modes demonstrate larger negative values of the mode Grüneisen parameters. Once Na is introduced in the framework of the material, it prefers to locate at the center of the quadrates of the framework material and binds to the four N anions nearby. As a consequence, the transverse vibrational mode of the CN group is clearly hindered and the NTE of the material is weakened. Our theoretical calculations have clarified the mechanisms of NTE and the effect of the guest Na on the NTE of the framework material. 展开更多
关键词 NEGATIVE thermal expansion(NTE) NA INSERTION FIRST-PRINCIPLES Calculations
Visible–light driven photocatalytic degradation of bisphenol-A using ultrasonically synthesized polypyrrole/K-birnessite nanohybrids:Experimental and DFT studies
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作者 Jannatun Zia Mohamed Ajeer Ufana Riaz 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第5期161-173,共13页
Although manganese oxides are known for their semiconductor characteristics, the photocatalytic performance of conducting polymer intercalated K-Birnessite(K-Bi) has not been explored till date. With the view to desig... Although manganese oxides are known for their semiconductor characteristics, the photocatalytic performance of conducting polymer intercalated K-Birnessite(K-Bi) has not been explored till date. With the view to design a visible light driven organic–inorganic hybrid photocatalyst for rapid degradation of Bisphenol A(BPA), the present work reports the ultrasound-assisted green synthesis of K-Bi/polypyrrole(Ppy) nanohybrids. The loading of Ppy in K-Bi was confirmed by thermogravimetric analysis while the formation of organic–inorganic hybrid was confirmed by infrared spectroscopy. K-Bi revealed a band gap of 2.8 e V while for the nanohybrids it was found to be ranging between 2.4 and 1.6 e V. X-ray diffraction studies confirmed partial intercalation of Ppy chains in the inter-layer space of K-Bi. High resolution transmission electron microscopy and scanning electron microscopy studies showed mixed morphology of K-Birnessite/Ppy nanohybrids. Rapid degradation of BPA was observed under visible irradiation in presence of K-Bi/Ppy nanohybrids and almost90% degradation of 20 mg/L BPA solution was achieved within 120 min. The degradation was found to follow pseudo-first order kinetics and the degraded fragments were identified using liquid chromatography-mass spectrometry. Degradation pathway was proposed based on density-functional theory calculations of fukui index predicting the radical easyattacking(f0) and(f-) sites in BPA. 展开更多
关键词 PHOTOCATALYSIS Degradation kinetics Manganese oxide POLYPYRROLE DFT calculations
Theoretical prediction on the reactivity of the Co-mediated intramolecular Pauson-Khand reaction for constructing bicyclo-skeletons in natural products
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作者 Lei Zhu Zheyuan Wang +4 位作者 Song Liu Tao Zhang Zhen Yang Ruopeng Bai Yu Lan 《中国化学快报:英文版》 SCIE CAS CSCD 2019年第4期889-894,共6页
The Co2(CO)8-mediated intramolecular Pauson-Khand reaction is an efficient approach for constructing polycyclic skeletons. Recently, some of us reported a series of this type reactions involving stericallyhindered eny... The Co2(CO)8-mediated intramolecular Pauson-Khand reaction is an efficient approach for constructing polycyclic skeletons. Recently, some of us reported a series of this type reactions involving stericallyhindered enynes for synthesizing natural products with reasonable reaction rates and yields. However, the reason for the high reactivity of the reaction remains unclear. We employed density functional theory calculations to clarify the mechanism and reactivity for this reaction. In contrast with chain olefin reactants, CO insertion is considered to be the rate-determining step for the overall Pauson-Khand reaction of cyclooctene derivatives. The reduced activation free energy for the alkene insertion step is attributed to:i) the electron-withdrawing group in close proximity to the C-C triple bond enhancing the reactivity of the alkyne moiety;ii) lower steric hindrance during alkene insertion when using the cyclooctene derivative. The effect of the substituent on the Co2(CO)8-mediated intramolecular PausonKhand reaction was then investigated. Internal alkenes exhibit lower reactivity than terminal alkenes because of the steric hindrance introduced by the substituted group. The cis internal alkene exhibits higher reactivity than the trans internal alkene. An ester group in close proximity to the C -C triple bond significantly enhances the reactivity. 展开更多
关键词 Pauson-Khand reaction Bicyclo-skeletons DFT CALCULATIONS Mechanism REACTIVITY
Investigation of Al2O3 and Fe2O3 transmission and transformation during the decomposition of phosphogypsum
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作者 Jie Yang Bin Zhu +1 位作者 Liping Ma Hongpan Liu 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2019年第5期1125-1131,共7页
Phosphogypsum(PG) is a solid waste produced in the phosphate fertilizer industry and is environmentally harmful.The decomposition of PG to recycle calcium and sulfur is a proper way to reutilize PG. Current work aims ... Phosphogypsum(PG) is a solid waste produced in the phosphate fertilizer industry and is environmentally harmful.The decomposition of PG to recycle calcium and sulfur is a proper way to reutilize PG. Current work aims at enriching the basic theory of coal decomposition process of PG. The emphasis was laid on the exploration of impact of main impurities on the process. On the other hand, according to Reaction Module, Equilib Module, and Phase Diagram Module of FactS age, the simulation computation was done on the systems of pure gypsum mixed with coal,with or without impurities for avoiding other impurities interference. Later, possible reactions in the process were deduced. Additionally, experiments were conducted in a TG-DTA integrated thermal gravimetric analyzer and a tube furnace. The products from the experiments were characterized and analyzed to verify the accuracy of theoretical calculations. The results showed that these impurities can change the decomposition process of PG. For example, aluminum oxide was transformed to calcium sulfoaluminate, while iron oxide was transformed to dicalcium ferrite. Furthermore, the results help to further improve the basic theory of phosphogypsum decomposition. 展开更多
关键词 PHOSPHOGYPSUM REDUCTIVE DECOMPOSITION Simulation calculations Aluminum OXIDE Iron OXIDE TERNARY DIAGRAM
Fine-tuning the ductile-brittle transition temperature of Mg2Si intermetallic compound via Al doping 预览
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作者 Ao Li Xin-peng Zhao +4 位作者 Hai-you Huang Yuan Ma Lei Gao Yan-jing Su Ping Qian 《矿物冶金与材料学报:英文版》 SCIE EI CAS CSCD 2019年第4期507-515,共9页
Brittleness is a dominant issue that restricts potential applications of Mg2Si intermetallic compounds(IMC).In this paper,guided by first-principles calculations,we found that Al doping will enhance the ductility of M... Brittleness is a dominant issue that restricts potential applications of Mg2Si intermetallic compounds(IMC).In this paper,guided by first-principles calculations,we found that Al doping will enhance the ductility of Mg2Si.The underlying mechanism is that Al doping could reduce the electronic exchange effect between Mg and Si atoms,and increase the volume module/shear modulus ratio,both of which are beneficial to the deformation capability of Mg2Si.Experimental investigations were then carried out to verify the calculation results with Al doping contents ranging from Al-free to 10wt%.Results showed that the obtained ductile-brittle transition temperature of the Mg2Si-Al alloy decreased and the corresponding ductility increased.Specifically,the ductile-brittle transition temperature could be reduced by about 100℃.When the content of Al reached 6wt%,α-Al phase started to precipitate,and the ductile-brittle transition temperature of the alloy no longer decreased. 展开更多
关键词 Mg alloy INTERMETALLIC compound FIRST-PRINCIPLES CALCULATIONS mechanical properties ductile-brittle transition temperature
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Thermodynamic Stability, Half-Metallic and Optical Properties of Sc2CoSi [001] Film:a DFT Study
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作者 Maliheh Amiri Hossein Akbari +4 位作者 Bashir Nedaee-shakarab Arash Boochani Amin Aminian Yousof Zangeneh Sirvan Naderi 《理论物理通讯:英文版》 SCIE CAS CSCD 2019年第4期455-462,共8页
The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the films thermodynamic stability of the [001] direction in f... The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the films thermodynamic stability of the [001] direction in four cases including:Sc-Sc, Sc-Co, Sc-Si and Co-Si terminations are studied using the ?rst principles calculations(FPLAPW) within the framework of the density functional theory(DFT). The band structure calculations represent the ferromagnetic halfmetallic properties with 100% spin polarization and 0.54 e V indirect gap in spin down for Sc2 CoSi bulk with optimized lattice parameters of 6.25 A?. The total magnetic moment obtained for this compound is-1.0 μB, which is in accordance with Slater-Pauling rule. The half-metallic(HM) behavior by 100% spin polarization at Fermi level is occurred in the Sc-Si termination with a 0.32 eV gap in down spin. The optical responses have been calculated for the bulk and ScSi termination by a red shift in these parameters and the metallic treatments have been increased. According to the thermodynamic phase diagrams, it is shown the Sc-Si and Sc-Sc terminations are more stable than other terminations. 展开更多
关键词 half-metalicity DFT THERMODYNAMIC stability THIN films HEUSLER alloy FIRST-PRINCIPLES calculations
Double dehydrogenation of carbocyclic β-dicarbonyl compounds:Koser’s reagent can do what iodine(V) reagents can
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作者 Shan-Shan Liu Li Wang +2 位作者 Ya-Nan Duan Ao Yu Chi Zhang 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第5期597-601,共5页
Koser’s reagent is found to be effective in the oxidative double dehydrogenation of various carbocyclic β-dicarbonyl compounds,which constitutes the first example on dehydrogenation reactivity of hypervalent iodine(... Koser’s reagent is found to be effective in the oxidative double dehydrogenation of various carbocyclic β-dicarbonyl compounds,which constitutes the first example on dehydrogenation reactivity of hypervalent iodine(Ⅲ) reagents for carbocyclic carbonyl compounds. DFT calculations reveal that the rate-determining step is the electrophilic addition of PhI+OH onto enolate of monodehydrogenated product. 展开更多
关键词 Koser’s REAGENT DOUBLE DEHYDROGENATION HYPERVALENT twisting 2 3-benzotropone DFT calculations
Polymetrical Analysis as Universal System of Formalization the Knowledge 预览
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作者 Petro P.Trokhimchuck 《数学和系统科学:英文版》 2019年第3期71-85,共15页
Problem of search of universal system of formalization the knowledge is discussed.Philisophical,mathematical,cybernetic and computing aspects of its problem are analyzed.Foundation of polymetrical analysis as variant ... Problem of search of universal system of formalization the knowledge is discussed.Philisophical,mathematical,cybernetic and computing aspects of its problem are analyzed.Foundation of polymetrical analysis as variant of resolution of this problem is represented.We show that this system allowed resolving S.Beer centurial problem in cybernetics.Also it allowed creating the natural(operational)approach in the foundation of mathematics and system concept of computing science. 展开更多
关键词 Polymetrical ANALYSIS S.Beer centurial problem TRIPLE optimization hybrid THEORY of systems THEORY of information calculations foundation of mathematics variable HIERARCHY metascience
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Exploration of the structural and optical properties of a red-emitting phosphor K2TiF6:Mn4+
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作者 豆喜龙 邝小渝 +1 位作者 夏欣欣 巨濛 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期544-549,共6页
The exploration of the appropriate red phosphor with good luminescence properties is an important issue in the development of current white light-emitting diode(WLED) devices. Transition metal Mn-doped compounds are f... The exploration of the appropriate red phosphor with good luminescence properties is an important issue in the development of current white light-emitting diode(WLED) devices. Transition metal Mn-doped compounds are fascinating luminescent materials. Herein, we performed a systematic theoretical study of the microstructure and optical properties of K2TiF6:Mn4+ using the CALYPSO structure search method in combination with first-principles calculations. We uncovered a novel structure of K2TiF6:Mn4+ with space group P-3m1 symmetry, where the impurity Mn4+ ions are accurately located at the center of the MnF6 octahedra. Based on our developed complete energy matrix diagonalization(CEMD)method, we calculated transition lines for 2Eg →4A2,4A2→4T2, and4A2→T2at 642 nm, 471 nm, and 352 nm,respectively, which are in good agreement with the available experimental data. More remarkably, we also found another transition(4A2→2T2) that lies at 380 nm, which should be a promising candidate for laser action. 展开更多
关键词 crystal structures FIRST-PRINCIPLES CALCULATIONS K2TiF6
Electronic and optical properties of GaN–MoS2 heterostructure from first-principles calculations
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作者 任达华 谭兴毅 +1 位作者 张腾 张源 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第8期254-257,共4页
Heterostructures(HSs)have attracted significant attention because of their interlayer van der Waals interactions.The electronic structures and optical properties of stacked GaN-MoS2 HSs under strain have been explored... Heterostructures(HSs)have attracted significant attention because of their interlayer van der Waals interactions.The electronic structures and optical properties of stacked GaN-MoS2 HSs under strain have been explored in this work using density functional theory.The results indicate that the direct band gap(1.95 e V)of the Ga N-MoS2 HS is lower than the individual band gaps of both the GaN layer(3.48 e V)and the MoS2 layer(2.03 eV)based on HSE06 hybrid functional calculations.Specifically,the GaN-MoS2 HS is a typical type-II band HS semiconductor that provides an effective approach to enhance the charge separation efficiency for improved photocatalytic degradation activity and water splitting efficiency.Under tensile or compressive strain,the direct band gap of the GaN-MoS2 HS undergoes redshifts.Additionally,the GaN-MoS2 HS maintains its direct band gap semiconductor behavior even when the tensile or compressive strain reaches 5%or-5%.Therefore,the results reported above can be used to expand the application of Ga N-MoS2 HSs to photovoltaic cells and photocatalysts. 展开更多
关键词 GaN-MoS2 HETEROSTRUCTURE electronic structures optical properties FIRST-PRINCIPLES CALCULATIONS
Effect of the alkali metal(Li, Na, K) substitution on the geometric,electronic and optical properties of the smallest diamondoid: First principles calculations
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作者 Sriprajak Krongsuk Nikorn Shinsuphan Vittaya Amornkitbumrung 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2019年第2期476-482,共7页
In this study we employed the B3LYP/6-311++G(d,p) method combined with the CIS/6-311++G(d,p) calculation to investigate the effects of the type and the number of alkali metal atoms(Li, Na, K) on the geometric, electro... In this study we employed the B3LYP/6-311++G(d,p) method combined with the CIS/6-311++G(d,p) calculation to investigate the effects of the type and the number of alkali metal atoms(Li, Na, K) on the geometric, electronic, and optical properties of alkali metals substituted into adamantanes. Substituting alkali metal(Li, Na, K)atoms caused significant changes in the electronic and optical properties of adamantane. The Ad-1Li, Ad-1Na,and Ad-1K structures showed a dramatically decreased energy gap and ionization potential, while adding more alkali metal atoms slightly decreased these properties. Substituting more alkali metals led to a shift in the maximum absorption wavelength from the visible to the infrared region, depending on the type of alkali metal atom substituted. The magnitude of shift occurred in the following order: Li b Na b K. These characteristics suggest the possibility of tunable electronic structures of this material for optoelectronic device applications. 展开更多
关键词 FUNCTIONALIZATION Electronic structure Molecular stability Bathochromic SHIFT DFT CALCULATIONS
Mechanical Properties of Formamidinium Halide Perovskites FABX3(FA=CH(NH2)2;B=Pb, Sn;X=Br, I) by First-Principles Calculations
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作者 郭磊 唐刚 洪家旺 《中国物理快报:英文版》 SCIE CAS CSCD 2019年第5期44-48,共5页
The mechanical properties of formamidinium halide perovskites FABX3(FA=CH(NH2)2;B=Pb, Sn;X=Br, I)are systematically investigated using first-principles calculations. Our results reveal that FABX3 perovskites possess e... The mechanical properties of formamidinium halide perovskites FABX3(FA=CH(NH2)2;B=Pb, Sn;X=Br, I)are systematically investigated using first-principles calculations. Our results reveal that FABX3 perovskites possess excellent mechanical flexibility, ductility and strong anisotropy. We shows that the planar organic cation FA+ has an important effect on the mechanical properties of FABX3 perovskites. In addition, our results indicate that (i) the moduli(bulk modulus B, Young’s modulus E, and shear modulus G) of FABBr3 are larger than those of FABI3 for the same B atom, and (ii) the moduli of FAPbX3 are larger than those of FASnX3 for the same halide atom. The reason for the two trends is demonstrated by carefully analyzing the bond strength between B and X atoms based on the projected crystal orbital Hamilton population method. 展开更多
关键词 FA=CH SN MECHANICAL Properties of Formamidinium HALIDE Perovskites FABX3 by First-Principles Calculations B FA CH
First-principles investigation of the concentration effect on equilibrium fractionation of Ca isotopes in forsterite
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作者 Yahui Song Yonghui Li +1 位作者 Wenzhong Wang Zhongqing Wu 《中国地球化学学报:英文版》 EI CAS CSCD 2019年第4期497-507,共11页
Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional the... Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional theory,we investigated how the average Ca–O bond length and the reduced partition function ratios(10^3 lnb)and103lna of 44 Ca/40 Ca in forsterite(Fo)are affected by its Ca concentration.Our results show that Ca–O bond length in forsterite ranges from 2.327 to 2.267 A with the Ca/(Ca+Mg)varying between a narrow range limited by an upper limit of 1/8 and a lower limit of 1/64.However,outside this narrow range,i.e.,Ca/(Ca+Mg)is lower than1/64 or higher than 1/8,Ca–O bond length becomes insensitive to Ca concentration and maintains to be a constant.Because the 10^3 lnb is negatively correlated with Ca–O bond length,the 10^3lnb significantly increases with decreasing Ca/(Ca+Mg)when 1/64<Ca/(Ca+Mg)<2/16.As a consequence,the 10^3lna between forsterite and other minerals also strongly depend on the Ca content in forsterite.Combining previous studies with our results,the heavier Ca isotopes enrichment sequence in minerals is:forsterite[orthopyroxene[clinopyroxene[calcite & diopside[dolomite[aragonite.Olivineand pyroxenes are enriched in heavier Ca isotope compared to carbonates.The 10^3lna between forsterite with a Ca/(Ca+Mg)of 1/64 and clinopyroxene(Ca/Mg=1/1,i.e.,diopside)is up to~0.64%at 1200 K.The large 103lnaFodiopsiderelative to the current analytical precision for Ca isotope measurements suggests that the dependence of10^3 lnaFo-diopsideon temperature can be used as a thermometer,similar to the one based on the 103lna of 44 Ca/40 Ca between orthopyroxene and diopside.These two Ca isotope thermometers both have a precision approximate to that of elemental thermometers and provide independent constraints on temperature. 展开更多
关键词 Ca ISOTOPE FIRST-PRINCIPLES CALCULATIONS FORSTERITE Concentration effect EQUILIBRIUM ISOTOPE FRACTIONATION
Band engineering of B2H2 nanoribbons
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作者 雷宝 张余洋 杜世萱 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第4期305-309,共5页
Freestanding honeycomb borophene is unstable due to the electron-deficiency of boron atoms. B2H2 monolayer, a typical borophene hydride, has been predicted to be structurally stable and attracts great attention. Here,... Freestanding honeycomb borophene is unstable due to the electron-deficiency of boron atoms. B2H2 monolayer, a typical borophene hydride, has been predicted to be structurally stable and attracts great attention. Here, we investigate the electronic structures of B2H2 nanoribbons. Based on first-principles calculations, we have found that all narrow armchair nanoribbons with and without mirror symmetry(ANR-s and ANR-as, respectively) are semiconducting. The energy gap has a relation with the width of the ribbon. When the ribbon is getting wider, the gap disappears. The zigzag ribbons without mirror symmetry(ZNR-as) have the same trend. But the zigzag ribbons with mirror symmetry(ZNR-s) are always metallic. We have also found that the metallic ANR-as and ZNR-s can be switched to semiconducting by applying a tensile strain along the nanoribbon. A gap of 1.10 eV is opened under 16% strain for the 11.0-■ ANR-as. Structural stability under such a large strain has also been confirmed. The flexible band tunability of B2H2 nanoribbon increases its possibility of potential applications in nanodevices. 展开更多
关键词 borophene HYDRIDE NANORIBBONS BAND ENGINEERING FIRST-PRINCIPLES CALCULATIONS strain
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