The ultra-low thermal conductivity of roughened silicon nanowires(SiNWs)can not be explained by the classical phonon-surface scattering mechanism.Although there have been several efforts at developing theories of phon...The ultra-low thermal conductivity of roughened silicon nanowires(SiNWs)can not be explained by the classical phonon-surface scattering mechanism.Although there have been several efforts at developing theories of phonon-surface scattering to interpret it,but the underlying reason is still debatable.We consider that the bond order loss and correlative bond hardening on the surface of roughened SiNWs will deeply influence the thermal transport because of their ultra-high surface-to-volume ratio.By combining this mechanism with the phonon Boltzmann transport equation,we explicate that the suppression of high-frequency phonons results in the obvious reduction of thermal conductivity of roughened SiNWs.Moreover,we verify that the roughness amplitude has more remarkable influence on thermal conductivity of SiNWs than the roughness correlation length,and the surface-to-volume ratio is a nearly universal gauge for thermal conductivity of roughened SiNWs.展开更多
The bond order and packing ratios in the single-crystal of the two structural polymorphs as well as the detailed electronic structures of the molecular model were studied using density functional theory. The strength ...The bond order and packing ratios in the single-crystal of the two structural polymorphs as well as the detailed electronic structures of the molecular model were studied using density functional theory. The strength of different Mn coordination bonds was analyzed in detail through Mayer bond order. Besides bond length, many other factors such as the orientation of ligand and nature of metal also significantly influence the bond order. Packing ratios cal- culated using cluster model reveals that packing along b direction in Dimer is more favorable than other directions due to the associated interactions of π-π and CI…H when packing in this direction. Electronic structure helps ex- plain the formation of Dimer from monomer or direct forming of Chain from ligand/Cl and metal. This would shed light on further understanding the importance of supramolecular interaction on crystal engineering.展开更多
meso-Tetrakis（4-aminophenyl）porphyrin（TAPP） can self-assemble into nanostructures with different morphologies by a phase-transfer method.The morphologies（nanospheres,nanorods and nanothorns）of porphyrin nanoaggr...meso-Tetrakis（4-aminophenyl）porphyrin（TAPP） can self-assemble into nanostructures with different morphologies by a phase-transfer method.The morphologies（nanospheres,nanorods and nanothorns）of porphyrin nanoaggregates could be easily tuned just by changing the concentration of porphyrin in a proper solvent at room temperature.HRTEM images revealed the formation of highly ordered supramolecular arrays of TAPP,i.e. superlattice of TAPP molecules in nanoaggregates,which agreed well with the size of one molecule of TAPP.UV–vis absorption spectra showed an obvious red shift of the Soret band of TAPP,indicating the formation of J-aggregates of TAPP in nanoaggregates.展开更多
Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, Erratum： Empirical potential for hydrocarbons for use in simu...Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, Erratum： Empirical potential for hydrocarbons for use in simulating the chemical vapor deposition of diamond films, Phys. Rev. B 1992, 46 1948]. In this paper, for the pure cupric element, the energy and structural parameters for several bulk phases as well as dimmer structure are well reproduced. The reference data are taken from our density functional theory calculations and the available experiments. The model potential also provides a good description of the bulk properties of various solid structures of cupric oxide compound structures, including cohesive energies, lattice parameters, and elastic constants.展开更多
Density functional theory（DFT） calculations are performed to investigate the reactivity of Th atom toward ethane C–C bond activation.A comprehensive description of the reaction mechanisms leading to two different r...Density functional theory（DFT） calculations are performed to investigate the reactivity of Th atom toward ethane C–C bond activation.A comprehensive description of the reaction mechanisms leading to two different reaction products is presented.We report a complete exploration of the potential energy surfaces by taking into consideration different spin states.In addition,the intermediate and transition states along the reaction paths are characterized.Total,partial,and overlap population density of state diagrams and analyses are also presented.Furthermore,the natures of the chemical bonding of intermediate and transition states are studied by using topological method combined with electron localization function（ELF） and Mayer bond order.Infrared spectrum（IR） is obtained and further discussed based on the optimized geometries.展开更多
Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths.Building on our recent work,in this paper we add further evidence on the...Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths.Building on our recent work,in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis.Presently reported results include atomic charges,natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC_(2k/2k+1)H chain family.They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes,e.g.,electron removal from or electron attachment to a neutral chain.Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC_(2k/2k+1)H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study.展开更多
The molecular behaviors of interfacial water molecules at the solid/liquid interface are of a fundamental significance in a diverse set of technical and scientific contexts,thus have drawn extensive attentions.On cert...The molecular behaviors of interfacial water molecules at the solid/liquid interface are of a fundamental significance in a diverse set of technical and scientific contexts,thus have drawn extensive attentions.On certain surfaces,the water monolayer may exhibit an ordered feature,which may result in the novel wetting phenomenon.In this article,based on the molecular dynamics simulations,we make a detailed structure analysis of the ordered water monolayer on ionic model surface with graphene-like hexagonal lattices under various charges and unit cell sizes.We carefully analyze the water density profiles and potential of mean force,which are the origin of the special hexagonal ordered water structures near the solid surface.The number of hydrogen bonds of the ordered water monolayer near the solid surface is carefully investigated.展开更多
The nanolaminated MAB phases have attracted great research interests due to their unusual combination of metal-like and ceramic-like properties, which is similar to MAX phases. Recently, ordered quaternary MAX phases ...The nanolaminated MAB phases have attracted great research interests due to their unusual combination of metal-like and ceramic-like properties, which is similar to MAX phases. Recently, ordered quaternary MAX phases have been discovered, which enriches the family of MAX phases, and opens a new window to tailor the properties of MAX phases and to develop new MXenes. In the present work, we explored possible ordered quaternary MAB phases with Cr3AlB4 structure(space group: Pmmm) by first-principles calculations. The predictions show that M2M’AlB4 phases with M = Mn, Fe, Co and M’ = Cr, Mo, W exhibit strong tendency of ordering, where M locates at 2t site(0.5, 0.5, z2t) and M’ locates at 1 g site(0, 0.5,0.5). The main driving force of ordering may be the differences in bonding strengths between Al and M elements. Analyses on chemical bonds reveal that bonding strengths increase following the order:Al-Mn < Al-Fe < Al-Co, which is consistent with the prediction that ordering tendency increases when M changes from Mn to Co, as derived from enthalpy differences. The ordered M2M’AlB4 phases with M =Mn or Fe are predicted ferromagnetic and ordered M2M’AlB4 phases display lower shear resistance and possibly better ductility in comparison to Cr3AlB4.展开更多
It has been well acknowledged that molecular water structures at the interface play an important role in the surface properties, such as wetting behavior or surface frictions. Using molecular dynamics simulation, we s...It has been well acknowledged that molecular water structures at the interface play an important role in the surface properties, such as wetting behavior or surface frictions. Using molecular dynamics simulation, we show that the water self-diffusion on the top of the first ordered water layer can be enhanced near a super-hydrophilic solid surface. This is attributed to the fewer number of hydrogen bonds between the first ordered water layer and water molecules above this layer, where the ordered water structures induce much slower relaxation behavior of water dipole and longer lifetime of hydrogen bonds formed within the first layer.展开更多
基金the National Natural Science Foundation of China(Grant No.11874145).
文摘The ultra-low thermal conductivity of roughened silicon nanowires(SiNWs)can not be explained by the classical phonon-surface scattering mechanism.Although there have been several efforts at developing theories of phonon-surface scattering to interpret it,but the underlying reason is still debatable.We consider that the bond order loss and correlative bond hardening on the surface of roughened SiNWs will deeply influence the thermal transport because of their ultra-high surface-to-volume ratio.By combining this mechanism with the phonon Boltzmann transport equation,we explicate that the suppression of high-frequency phonons results in the obvious reduction of thermal conductivity of roughened SiNWs.Moreover,we verify that the roughness amplitude has more remarkable influence on thermal conductivity of SiNWs than the roughness correlation length,and the surface-to-volume ratio is a nearly universal gauge for thermal conductivity of roughened SiNWs.
基金This work was supported by the National ScienceFoundation for Distinguished Young Scholars of China （No. 21525101）, the National Science Foundation of China and Guangxi Province （Nos. 91122032, 2014GXNSFFA118003）, the BAGUI scholar program （No. 2014A001）, the Project of Talents Highland of Guangxi Province, and Hubei University. This work is also supported by Opening Project of Wuhan National High Magnetic Field Center （No. 2015KF05）, and Huazhong University of Science and Technology. We acknowledge the group of Professor Jianzhuang Jiang （University of Science and Technology Beijing： USTB） for providing computational resources and thank Dr. Dongdong Qi for stimulating discussions.
文摘The bond order and packing ratios in the single-crystal of the two structural polymorphs as well as the detailed electronic structures of the molecular model were studied using density functional theory. The strength of different Mn coordination bonds was analyzed in detail through Mayer bond order. Besides bond length, many other factors such as the orientation of ligand and nature of metal also significantly influence the bond order. Packing ratios cal- culated using cluster model reveals that packing along b direction in Dimer is more favorable than other directions due to the associated interactions of π-π and CI…H when packing in this direction. Electronic structure helps ex- plain the formation of Dimer from monomer or direct forming of Chain from ligand/Cl and metal. This would shed light on further understanding the importance of supramolecular interaction on crystal engineering.
基金financially supported by the National Natural Science Foundation of China(Nos.51042013,21271119)Innovation Fund of Shanghai(No.10170502400)+1 种基金Science Foundation of Shandong Provincial Education Department(No.J08LC11)Research Progect of‘‘SUST Spring Bud’’(No.2008BWZ056)
文摘meso-Tetrakis（4-aminophenyl）porphyrin（TAPP） can self-assemble into nanostructures with different morphologies by a phase-transfer method.The morphologies（nanospheres,nanorods and nanothorns）of porphyrin nanoaggregates could be easily tuned just by changing the concentration of porphyrin in a proper solvent at room temperature.HRTEM images revealed the formation of highly ordered supramolecular arrays of TAPP,i.e. superlattice of TAPP molecules in nanoaggregates,which agreed well with the size of one molecule of TAPP.UV–vis absorption spectra showed an obvious red shift of the Soret band of TAPP,indicating the formation of J-aggregates of TAPP in nanoaggregates.
基金Project supported by the Doctoral Program of Higher Education of China(Grant No.20111415120002)the National Natural Science Foundation of China(Grant Nos.11204199,61178067,and 51135007)+1 种基金the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province,Chinathe Youth Foundation of Taiyuan University of Science and Technology,China(Grant No.20113020)
文摘Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, Erratum： Empirical potential for hydrocarbons for use in simulating the chemical vapor deposition of diamond films, Phys. Rev. B 1992, 46 1948]. In this paper, for the pure cupric element, the energy and structural parameters for several bulk phases as well as dimmer structure are well reproduced. The reference data are taken from our density functional theory calculations and the available experiments. The model potential also provides a good description of the bulk properties of various solid structures of cupric oxide compound structures, including cohesive energies, lattice parameters, and elastic constants.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21371160,21401173,and 11364023)
文摘Density functional theory（DFT） calculations are performed to investigate the reactivity of Th atom toward ethane C–C bond activation.A comprehensive description of the reaction mechanisms leading to two different reaction products is presented.We report a complete exploration of the potential energy surfaces by taking into consideration different spin states.In addition,the intermediate and transition states along the reaction paths are characterized.Total,partial,and overlap population density of state diagrams and analyses are also presented.Furthermore,the natures of the chemical bonding of intermediate and transition states are studied by using topological method combined with electron localization function（ELF） and Mayer bond order.Infrared spectrum（IR） is obtained and further discussed based on the optimized geometries.
基金financial support from the German Research Foundation(DFG Grant No.BA 1799/3-2)in the initial stage of this work and computational support by the state of Baden-Württemberg through bw HPC and the German Research Foundation through Grant No.INST 40/575-1 FUGG(bw Uni Cluster 2.0,bw For Cluster/MLS&WISO 2.0/HELIX,and JUSTUS 2.0 cluster)
文摘Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths.Building on our recent work,in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis.Presently reported results include atomic charges,natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC_(2k/2k+1)H chain family.They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes,e.g.,electron removal from or electron attachment to a neutral chain.Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC_(2k/2k+1)H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study.
基金Supported by the National Science Foundation of China(Nos.11290164and 11204341)the Knowledge Innovation Program of SINAP+2 种基金the Knowledge Innovation Program of the Chinese Academy of SciencesShanghai Supercomputer Center of ChinaSupercomputing Center of Chinese Academy of Science
文摘The molecular behaviors of interfacial water molecules at the solid/liquid interface are of a fundamental significance in a diverse set of technical and scientific contexts,thus have drawn extensive attentions.On certain surfaces,the water monolayer may exhibit an ordered feature,which may result in the novel wetting phenomenon.In this article,based on the molecular dynamics simulations,we make a detailed structure analysis of the ordered water monolayer on ionic model surface with graphene-like hexagonal lattices under various charges and unit cell sizes.We carefully analyze the water density profiles and potential of mean force,which are the origin of the special hexagonal ordered water structures near the solid surface.The number of hydrogen bonds of the ordered water monolayer near the solid surface is carefully investigated.
基金supported by National Natural Science Foundation of China under Grant No. U1435206 and No. 51672064
文摘The nanolaminated MAB phases have attracted great research interests due to their unusual combination of metal-like and ceramic-like properties, which is similar to MAX phases. Recently, ordered quaternary MAX phases have been discovered, which enriches the family of MAX phases, and opens a new window to tailor the properties of MAX phases and to develop new MXenes. In the present work, we explored possible ordered quaternary MAB phases with Cr3AlB4 structure(space group: Pmmm) by first-principles calculations. The predictions show that M2M’AlB4 phases with M = Mn, Fe, Co and M’ = Cr, Mo, W exhibit strong tendency of ordering, where M locates at 2t site(0.5, 0.5, z2t) and M’ locates at 1 g site(0, 0.5,0.5). The main driving force of ordering may be the differences in bonding strengths between Al and M elements. Analyses on chemical bonds reveal that bonding strengths increase following the order:Al-Mn < Al-Fe < Al-Co, which is consistent with the prediction that ordering tendency increases when M changes from Mn to Co, as derived from enthalpy differences. The ordered M2M’AlB4 phases with M =Mn or Fe are predicted ferromagnetic and ordered M2M’AlB4 phases display lower shear resistance and possibly better ductility in comparison to Cr3AlB4.
基金supported by the National Natural Science Foundation of China(Grant Nos.11290164,11674345,and U1532260)the Key Research Program of Chinese Academy of Sciences(Grant Nos.KJZD-EW-M03 and QYZDJ-SSW-SLH019)+3 种基金the Youth Innovation Promotion Association,Chinese Academy of Sciences,the Shanghai Supercomputer Center of Chinathe Computer Network Information Center of Chinese Academy of Sciencesthe Special Program for Applied Research on Super Computation of the NSFC–Guangdong Joint Fund(the second phase)China
文摘It has been well acknowledged that molecular water structures at the interface play an important role in the surface properties, such as wetting behavior or surface frictions. Using molecular dynamics simulation, we show that the water self-diffusion on the top of the first ordered water layer can be enhanced near a super-hydrophilic solid surface. This is attributed to the fewer number of hydrogen bonds between the first ordered water layer and water molecules above this layer, where the ordered water structures induce much slower relaxation behavior of water dipole and longer lifetime of hydrogen bonds formed within the first layer.
