The density functional theory （DFT） is the most popular method for evaluating bond dis- sociation enthalpies （BDEs） of most molecules. Thus, we are committed to looking for alternative methods that can balance the...The density functional theory （DFT） is the most popular method for evaluating bond dis- sociation enthalpies （BDEs） of most molecules. Thus, we are committed to looking for alternative methods that can balance the computational cost and higher precision to the best for large systems. The performance of DFT, double-hybrid DFT, and high-level com- posite methods are examined. The tested sets contain monocyclic and polycyclic aromatic molecules, branched hydrocarbons, small inorganic molecules, etc. The results show that the mPW2PLYP and G4MP2 methods achieve reasonable agreement with the benchmark val- ues for most tested molecules, and the mean absolute deviations are 2.43 and 1.96 kcal/mol after excluding the BDEs of branched hydrocarbons. We recommend the G4MP2 is the most appropriate method for small systems （atoms number≤20）; the double-hybrid DFT methods are advised for large aromatic molecules in medium size （20≤atoms number≤50）, and the double-hybrid DFT methods with empirical dispersion correction are recommended for long-chain and branched hydrocarbons in the same size scope; the DFT methods are ad- vised to apply for large systems （atoms number〉50）, and the M06-2X and B3P86 methods are also favorable. Moreover, the differences of optimized geometry of different methods are discussed and the effects of basis sets for various methods are investigated.展开更多
By introducing the functional theory into the calculation of electric double layer （EDL） interaction, the interaction energies of two parallel plates were calculated respectively at low, moderate, and high potential...By introducing the functional theory into the calculation of electric double layer （EDL） interaction, the interaction energies of two parallel plates were calculated respectively at low, moderate, and high potentials. Compared with the results of two existing methods, Debye-Hückel and Langmuir methods, which are applicable just to the critical potentials and perform poorly in the intermediate potential, the functional approach not only has much simpler expression of the EDL interaction energy, but also performs well in the entire range of potentials.展开更多
The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design ...The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design the M^+-M^+single bond.Existing studies generally use sterically bulky organic ligands L^-to synthesize the compounds in the L^--M^+-M^+-L-manner.However,here we report the design of Mg-Mg and Zn-Zn single bonds in two ligandless clusters,Mg2B7-and Zn2B7-,using density functional theory methods.The global minima of both of the clusters are in the form of M2^2+(B7^3-),where the M-M single bonds are positioned above a quasi-planar hexagonal B7 moiety.Chemical bonding analyses further confirm the existence of Mg-Mg and Zn-Zn single bonds in these clusters,which are driven by the unusually stable B7^3-moiety that is bothσandπaromatic.Vertical detachment energies of Mg2B7-and Zn2B7-are calculated to be 2.79 e V and 2.94 e V,respectively,for the future comparisons with experimental data.展开更多
As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the...As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the behavior of double 6-membered rings(D6Rs)in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation.For the transformation of FAU to CHA,because both zeolites contain the same D6R units,direct transformation occurs,in which the D6Rs were largely unchanged.In contrast,for the transformation of FAU to MFI,the D6Rs can be divided into two single 6-membered rings(S6Rs),which further assembled into the MFI structure.In this crystallization,5-membered rings(5Rs)are only observed in the MFI framework formation,suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs.These insights will be helpful for further understanding of the interzeolite transformation.展开更多
Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide(CO2)emission into the environment.It has been found that the amine-based organic molecules could absorb CO_(2) efficiently...Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide(CO2)emission into the environment.It has been found that the amine-based organic molecules could absorb CO_(2) efficiently and form the bicarbonate salts through hydrogen-bond(H-bond)interactions.Recently,the aqueous 1,3-diphenylguanidine(DPG)solution was developed to trap and convert CO_(2) to valuable chemicals under ambient conditions.However,how the DPG molecules interact with CO_(2) in an aqueous solution remains unclear.In this work,we perform molecular dynamics simulations to explore the atomistic details of CO_(2) in the aqueous DPG.The simulated results reveal that the protonated DPGH+and the bicarbonate anions prefer to form complexes through different H-bond patterns.These double H-bonds are quite stable in thermodynamics,as indicated from the accurate density functional theory calculations.This study is helpful to understand the catalytic mechanism of CO_(2) conversion in the aqueous DPG.展开更多
Accurate description of potential energy curves driven by nonbonded interactions remains a great challenge for pure density functional approximations(DFAs).It is because the Rdecay behavior of dispersion cannot be int...Accurate description of potential energy curves driven by nonbonded interactions remains a great challenge for pure density functional approximations(DFAs).It is because the Rdecay behavior of dispersion cannot be intrinsically captured by the(semi)-local ingredients and the exact-exchange used in the popular hybrid DFAs.Overemphasizing the accuracy on the equilibrium region for the functional construction would likely deteriorate the overall performance on the other regions of potential energy surfaces.In consequence,the empirical dispersion correction becomes the standard component in DFAs to treat the non-bonded interactions.In this Letter,we demonstrate that without the use of empirical dispersion correction,doubly hybrid approximations,in particular two recently proposed rev XYG3 and XYG7 functionals,hold the promise to have a balanced description of non-bonded interactions on the whole potential energy curves for several prototypes ofπ-π,CH/π,and SH/πinteractions.The error of rev XYG3 and XYG7 for non-bonded interactions is around 0.1 kcal/mol,and their potential energy curves almost coincide with the accurate CCSD(T)/CBS curves.展开更多
Variable supply voltage-clustered voltage scaling （VS-CVS） scheme can be very effective in reducing power consumption of CMOS circuits without degrading system performance. Level converting flip-flops （LCFFs） are ...Variable supply voltage-clustered voltage scaling （VS-CVS） scheme can be very effective in reducing power consumption of CMOS circuits without degrading system performance. Level converting flip-flops （LCFFs） are key elements in the CVS scheme. In this paper, a new explicit-pulsed double-edge triggered level converting flip-flop （nEP-DET-LCFF） is proposed, which employs double-edge triggering technique, dynamic structure, explicit pulse generator, conditional discharge technique and proper arrangement of stacked nMOS transistors to efficiently perform latching and level converting functions simultaneously. The proposed nEP-DET-LCFF combines merits of both conventional explicit-LCFFs and implicit-LCFFs. Simulation shows the proposed nEP-DET-LCFF has improvement of 19.2% -46% in delay, and 19.4% - 52.9% in power-delay product （PDP） as compared with the published LCFFs.展开更多
Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the...Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the latter is more favorable for the Li storage and the former will evolve into the latter with the intercalation of Li ions. The relationship between the interlayer dis- tance of two graphene sheets and the intercalated capacity of Li ions is discussed, It is found that structural defect is identified to store Li ions more favorably than pristine bilayer graphene and an isolated C atom vacancy in bilayer graphene can capture three Li ions between two graphene sheets.展开更多
By means of the continuous Glimm functional, a proof is given on the global existence of classical solutions to Cauchy problem for general first order quasilinear hyperbolic systems with small initial total variation.
The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase （2,3QD） has been investigated by means of hy- brid density functional theory. The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by in...The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase （2,3QD） has been investigated by means of hy- brid density functional theory. The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by incorporation of both oxygen atoms into the substrate and releases carbon monoxide. The calculations show that dioxygen attack on the copper complex is energetically favorable. The adduct has a possible near-degeneracy of states between [Cu2＋-（substrate H＋）] and [Cu＋-（sub- strate-H）. ], and in addition the pyramidalized C2 atom is ideally suited for forming a dioxygembridged structure. In the next step, the C3-C4 bond is cleaved and intermediate lnt5 is formed via transition state TS4. Finally, the Oa-Ob and C2-C3 bonds are cleaved, and CO is released in one concerted transition state （TS5） with the barrier of 63.25 and 61.91 k J/tool in the gas phase and protein environments, respectively. On the basis of our proposed reaction mechanism, this is the rate-limiting step of the whole catalytic cycle and is strongly driven by a relatively large exothermicity of 100.86 kJ/mol. Our work provides some valuable fundamental insights into the behavior of this enzyme.展开更多
This paper is proposed to understand the interaction of porphyrin layers with diatomic molecules interacting at their interior regions by applying ab initio and density functional theory （DFT） methods. We have used ...This paper is proposed to understand the interaction of porphyrin layers with diatomic molecules interacting at their interior regions by applying ab initio and density functional theory （DFT） methods. We have used NO, GO, and O2 diatomic molecules to interact with the porphyrin layers. The most common Fe-centered metalloporphyrin structure with tetra-pyrrlic rings having N4 core is chosen for the study. The optimization of Porphyrin-Porphyrin （PI-PII） and Porphyrin-Diatomic molecule-Porphyrin （P1-AB-P11） （AB = NO, CO, and 02） complexes are performed using HF method. In order to understand the planarity and appropriate stacking size of porphyrins and also to infer the separation of diatomic molecules between porphyrin layers the behavior of PI-AB-PH complexes （where AB = NO, CO, and 02） are analyzed using structural properties and molecular electrostatic potentials （MEP）. The MEPs are caiculated using hybrid exchange correlation functional B3PW91 of DFT Mong with 6-31＋G basis set for the PI-PH and PI-AB-Pzz complexes obtained from HF method.展开更多
文摘The density functional theory （DFT） is the most popular method for evaluating bond dis- sociation enthalpies （BDEs） of most molecules. Thus, we are committed to looking for alternative methods that can balance the computational cost and higher precision to the best for large systems. The performance of DFT, double-hybrid DFT, and high-level com- posite methods are examined. The tested sets contain monocyclic and polycyclic aromatic molecules, branched hydrocarbons, small inorganic molecules, etc. The results show that the mPW2PLYP and G4MP2 methods achieve reasonable agreement with the benchmark val- ues for most tested molecules, and the mean absolute deviations are 2.43 and 1.96 kcal/mol after excluding the BDEs of branched hydrocarbons. We recommend the G4MP2 is the most appropriate method for small systems （atoms number≤20）; the double-hybrid DFT methods are advised for large aromatic molecules in medium size （20≤atoms number≤50）, and the double-hybrid DFT methods with empirical dispersion correction are recommended for long-chain and branched hydrocarbons in the same size scope; the DFT methods are ad- vised to apply for large systems （atoms number〉50）, and the M06-2X and B3P86 methods are also favorable. Moreover, the differences of optimized geometry of different methods are discussed and the effects of basis sets for various methods are investigated.
基金This work was supported by the National Natural Science Foundation of China （No.20676051 and No.20573048） and the Important Construction Project （category A） of Shanghai Jiao Tong University （No.AE150085）.
文摘By introducing the functional theory into the calculation of electric double layer （EDL） interaction, the interaction energies of two parallel plates were calculated respectively at low, moderate, and high potentials. Compared with the results of two existing methods, Debye-Hückel and Langmuir methods, which are applicable just to the critical potentials and perform poorly in the intermediate potential, the functional approach not only has much simpler expression of the EDL interaction energy, but also performs well in the entire range of potentials.
基金supported by the National Key R&D Program of China(No.2018YFE0115000)the Natural Science Foundation of Tianjin City(No.19JCYBJC19600)。
文摘The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design the M^+-M^+single bond.Existing studies generally use sterically bulky organic ligands L^-to synthesize the compounds in the L^--M^+-M^+-L-manner.However,here we report the design of Mg-Mg and Zn-Zn single bonds in two ligandless clusters,Mg2B7-and Zn2B7-,using density functional theory methods.The global minima of both of the clusters are in the form of M2^2+(B7^3-),where the M-M single bonds are positioned above a quasi-planar hexagonal B7 moiety.Chemical bonding analyses further confirm the existence of Mg-Mg and Zn-Zn single bonds in these clusters,which are driven by the unusually stable B7^3-moiety that is bothσandπaromatic.Vertical detachment energies of Mg2B7-and Zn2B7-are calculated to be 2.79 e V and 2.94 e V,respectively,for the future comparisons with experimental data.
基金supported by the National Key R&D Program of China(2017YFB0702800)the National Natural Science Foundation of China(2152780065,91634201 and 21720102001)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB17000000)~~
文摘As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the behavior of double 6-membered rings(D6Rs)in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation.For the transformation of FAU to CHA,because both zeolites contain the same D6R units,direct transformation occurs,in which the D6Rs were largely unchanged.In contrast,for the transformation of FAU to MFI,the D6Rs can be divided into two single 6-membered rings(S6Rs),which further assembled into the MFI structure.In this crystallization,5-membered rings(5Rs)are only observed in the MFI framework formation,suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs.These insights will be helpful for further understanding of the interzeolite transformation.
基金supported by the National Natural Science Foundation of China(No.21973015 and No.22125301)。
文摘Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide(CO2)emission into the environment.It has been found that the amine-based organic molecules could absorb CO_(2) efficiently and form the bicarbonate salts through hydrogen-bond(H-bond)interactions.Recently,the aqueous 1,3-diphenylguanidine(DPG)solution was developed to trap and convert CO_(2) to valuable chemicals under ambient conditions.However,how the DPG molecules interact with CO_(2) in an aqueous solution remains unclear.In this work,we perform molecular dynamics simulations to explore the atomistic details of CO_(2) in the aqueous DPG.The simulated results reveal that the protonated DPGH+and the bicarbonate anions prefer to form complexes through different H-bond patterns.These double H-bonds are quite stable in thermodynamics,as indicated from the accurate density functional theory calculations.This study is helpful to understand the catalytic mechanism of CO_(2) conversion in the aqueous DPG.
基金supported by the National Natural Science Foundation of China(No.21973015,No.22125301,No.91427301)the Science Challenge Project(TZ2018004)+1 种基金Innovative Research Team of High-Level Local universities in Shanghaia Key Laboratory Program of the Education Commission of Shanghai Municipality(ZDSYS14005)。
文摘Accurate description of potential energy curves driven by nonbonded interactions remains a great challenge for pure density functional approximations(DFAs).It is because the Rdecay behavior of dispersion cannot be intrinsically captured by the(semi)-local ingredients and the exact-exchange used in the popular hybrid DFAs.Overemphasizing the accuracy on the equilibrium region for the functional construction would likely deteriorate the overall performance on the other regions of potential energy surfaces.In consequence,the empirical dispersion correction becomes the standard component in DFAs to treat the non-bonded interactions.In this Letter,we demonstrate that without the use of empirical dispersion correction,doubly hybrid approximations,in particular two recently proposed rev XYG3 and XYG7 functionals,hold the promise to have a balanced description of non-bonded interactions on the whole potential energy curves for several prototypes ofπ-π,CH/π,and SH/πinteractions.The error of rev XYG3 and XYG7 for non-bonded interactions is around 0.1 kcal/mol,and their potential energy curves almost coincide with the accurate CCSD(T)/CBS curves.
基金Supported by the National Natural Science Foundation of China （No.60503027） Acknowledgements： The authors are grateful to Prof. Zhao PeiYi of Chapman University, Orange, USA, for beneficial discussions.
文摘Variable supply voltage-clustered voltage scaling （VS-CVS） scheme can be very effective in reducing power consumption of CMOS circuits without degrading system performance. Level converting flip-flops （LCFFs） are key elements in the CVS scheme. In this paper, a new explicit-pulsed double-edge triggered level converting flip-flop （nEP-DET-LCFF） is proposed, which employs double-edge triggering technique, dynamic structure, explicit pulse generator, conditional discharge technique and proper arrangement of stacked nMOS transistors to efficiently perform latching and level converting functions simultaneously. The proposed nEP-DET-LCFF combines merits of both conventional explicit-LCFFs and implicit-LCFFs. Simulation shows the proposed nEP-DET-LCFF has improvement of 19.2% -46% in delay, and 19.4% - 52.9% in power-delay product （PDP） as compared with the published LCFFs.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50802089 and 51072183)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China (Grant No. [2008] 890)the Natural Science Foundation of Zhejiang Province (Grant No. Y4090280)
文摘Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the latter is more favorable for the Li storage and the former will evolve into the latter with the intercalation of Li ions. The relationship between the interlayer dis- tance of two graphene sheets and the intercalated capacity of Li ions is discussed, It is found that structural defect is identified to store Li ions more favorably than pristine bilayer graphene and an isolated C atom vacancy in bilayer graphene can capture three Li ions between two graphene sheets.
文摘By means of the continuous Glimm functional, a proof is given on the global existence of classical solutions to Cauchy problem for general first order quasilinear hyperbolic systems with small initial total variation.
基金supported by the National Natural Science Foundation of China (21073164,20673098)the Natural Science Foundation of Zhejiang Province (Y4100620)the Research Foundation of the Education Bureau of Zhejiang Province (Y200906517)
文摘The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase （2,3QD） has been investigated by means of hy- brid density functional theory. The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by incorporation of both oxygen atoms into the substrate and releases carbon monoxide. The calculations show that dioxygen attack on the copper complex is energetically favorable. The adduct has a possible near-degeneracy of states between [Cu2＋-（substrate H＋）] and [Cu＋-（sub- strate-H）. ], and in addition the pyramidalized C2 atom is ideally suited for forming a dioxygembridged structure. In the next step, the C3-C4 bond is cleaved and intermediate lnt5 is formed via transition state TS4. Finally, the Oa-Ob and C2-C3 bonds are cleaved, and CO is released in one concerted transition state （TS5） with the barrier of 63.25 and 61.91 k J/tool in the gas phase and protein environments, respectively. On the basis of our proposed reaction mechanism, this is the rate-limiting step of the whole catalytic cycle and is strongly driven by a relatively large exothermicity of 100.86 kJ/mol. Our work provides some valuable fundamental insights into the behavior of this enzyme.
基金the Science and Engineering Research Board (SERB), India for awarding the fast track project (Project No: SB/FTP/PS-096/2013)
文摘This paper is proposed to understand the interaction of porphyrin layers with diatomic molecules interacting at their interior regions by applying ab initio and density functional theory （DFT） methods. We have used NO, GO, and O2 diatomic molecules to interact with the porphyrin layers. The most common Fe-centered metalloporphyrin structure with tetra-pyrrlic rings having N4 core is chosen for the study. The optimization of Porphyrin-Porphyrin （PI-PII） and Porphyrin-Diatomic molecule-Porphyrin （P1-AB-P11） （AB = NO, CO, and 02） complexes are performed using HF method. In order to understand the planarity and appropriate stacking size of porphyrins and also to infer the separation of diatomic molecules between porphyrin layers the behavior of PI-AB-PH complexes （where AB = NO, CO, and 02） are analyzed using structural properties and molecular electrostatic potentials （MEP）. The MEPs are caiculated using hybrid exchange correlation functional B3PW91 of DFT Mong with 6-31＋G basis set for the PI-PH and PI-AB-Pzz complexes obtained from HF method.
