在昆明西山国家森林公园地盘松林连续分布区内设置样地,并将样地内的地表凋落物分成枯枝、凋落物上层和凋落物下层3层,通过外业调查采集样品,在实验室测定载量、热值等相关燃烧能量参数,以单位面积热量为关键指标研究地盘松林地表凋落...在昆明西山国家森林公园地盘松林连续分布区内设置样地,并将样地内的地表凋落物分成枯枝、凋落物上层和凋落物下层3层,通过外业调查采集样品,在实验室测定载量、热值等相关燃烧能量参数,以单位面积热量为关键指标研究地盘松林地表凋落物的潜在能量。结果表明,在地盘松林地表凋落物中,凋落物上层、下层和枯枝的单位面积热量最大值差异不大,分别为51 866.3 k J/m2、48 942.13 k J/m2和42 611.53 k J/m2;平均值的差异也不大,分别为38 688.5 k J/m2、39 716.63 k J/m2和25 796.23 k J/m2。但最低值的差异却非常明显,凋落物上层的为25 510.8 k J/m2,枯枝的为8 980.93 k J/m2,凋落物下层的为30 491.1 k J/m2。展开更多
The close-coupling method is utilized to calculate partial cross sections for elastic and inelastic scattering of He atoms with HX （X=F, Cl, Br） molecule based on the CCSD （T） potential energy surfaces obtained in...The close-coupling method is utilized to calculate partial cross sections for elastic and inelastic scattering of He atoms with HX （X=F, Cl, Br） molecule based on the CCSD （T） potential energy surfaces obtained in the previous research. The calculation is performed at the incident energy of 200 me V. The rationality of our results has been confirmed by comparison with the available theoretical results. The tendency of the elastic and inelastic rotational excitation partial wave cross sections varying with the reduced mass of the three systems is obtained.展开更多
We study the ground state properties, potential energy curves and potential energy surfaces of the superheavy nucleus270 Hs by using the multidimensionally-constrained relativistic mean-field model with the effective ...We study the ground state properties, potential energy curves and potential energy surfaces of the superheavy nucleus270 Hs by using the multidimensionally-constrained relativistic mean-field model with the effective interaction PC-PK1. The binding energy,size and shape as well as single particle shell structure corresponding to the ground state of this nucleus are obtained.270 Hs is well deformed and exhibits deformed doubly magic feature in the single neutron and proton level schemes. One-dimensional potential energy curves and two-dimensional potential energy surfaces are calculated for270 Hs with various spatial symmetries imposed. We investigate in detail the effects of the reflection asymmetric and triaxial distortions on the fission barrier and fission path of270 Hs. When the axial symmetry is imposed, the reflection symmetric and reflection asymmetric fission barriers both show a double-hump structure and the former is higher. However, when triaxial shapes are allowed the reflection symmetric barrier is lowered very much and then the reflection symmetric fission path becomes favorable.展开更多
The structures of closo-hedral cluster (HAlNH)12 and endohedral complexes X@(HAlNH)12 (X = He, Ne, Ar, Kr) have been studied by using density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natura...The structures of closo-hedral cluster (HAlNH)12 and endohedral complexes X@(HAlNH)12 (X = He, Ne, Ar, Kr) have been studied by using density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natural bond orbital (NBO), vibrational frequency, energetic parameters, magnetic shielding constants and nucleus independent chemical shifts (NICS) were discussed. The potential surface of guest X shifting from the cage center to a face of six- membered ring was calculated at the same level. The exit transition state was demonstrated with IRC calculations. It is found that X@(HAlNH)12 complexes are dynamically stable, and Ne@(HAlNH)12 is more energetically favorable than the other complexes in thermodynamics.展开更多
When surface potential of the particles,ψ ,is high,sinh y can be approximated by≈ ey/2 in the nonlinear Poisson Boltzmann equation.Thus,we present a simple method of calculating the interaction force and energy per ...When surface potential of the particles,ψ ,is high,sinh y can be approximated by≈ ey/2 in the nonlinear Poisson Boltzmann equation.Thus,we present a simple method of calculating the interaction force and energy per unit area between two dissimilar plates with high potentials at constant surface potential.These formulae could be applicable to the case of repulsive case,in which the derivative of y must vanish at an interior point,and a minimum ymin=u always exists.A turning point at～κ h≈ 2(π－ 1)e－ y1/2 for the repulsion or attraction between dissimilar planar surfaces.These formulae are divergent atκ h∞ ,and zero point atκ h≈ 2π .This means that they can only be used atκ h < 2π and accurate location is atκ h≤ 4. Agreement of the approximation for force,Eq.（ 13） ,is good with the exact numerical values of the interaction of dissimilar plates given by Devereux [6] for high surface potentials.For y1≥ 5κ h≤ 3.0 the relative errors of Eq.(13) are less than 5％ ,and forκ h≤ 3.5 relative errors are less than 10％ .For the interaction energy,Eq.(15),the applicable range extends toκ h=4.0.Beyond this range the error increases rapidly.The higher surface potential is the better the precision of Eq.（ 13） and Eq.( 15).The condition of the strong interaction has been satisfied.展开更多
Some stationary points on the potential energy surface of [Si, N, N, P] system were located at the B3LYP/6-311G(d) and QCISD(t)/6-311+G(2df)(single-point) levels of theory, while the isomerization, structures, and sta...Some stationary points on the potential energy surface of [Si, N, N, P] system were located at the B3LYP/6-311G(d) and QCISD(t)/6-311+G(2df)(single-point) levels of theory, while the isomerization, structures, and stability of these obtained isomers were suggested. The computed results indicate that only four-membered ring isomer SiNPN(E1, 2A'), which possesses butterfly-like structure and Si-P cross bonding, is kinetically stable in all optimized isomers. Other isomers may be considered as kinetically unstable towards isomerization or dissociation because of the corresponding smaller reaction barriers. Furthermore, the present paper also proposes electronic and geometric structures, vibrational frequencies and the corresponding vibrational modes, dipole moments, and rotational constants of isomer E1. To make use of the computed results, we can clearly know that the reaction pathway via an intermediate E3 (SiNPN) is the most favorable channel producing isomer E1 from fragments SiN(2Π) and PN (1Σ), which have been well characterized in space, and thus, isomer E1 can be considered as a candidate for interstellar observation. The reaction enthalpy of SiN(2Π) + PN(1Σ)→ E1 and the standard enthalpy of formation of isomer E1 are 215.25 and 457.99 kJ/mol, respectively, at 298.15 K. Keywords potential energy surface - [Si,N,N,P] system - isomerization - kinetic stability展开更多
The potential energy surface of HPO2 system including eight isomers and twelve transition states is predicated at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df,2p)(single-point) levels of theory. On the potential energ...The potential energy surface of HPO2 system including eight isomers and twelve transition states is predicated at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df,2p)(single-point) levels of theory. On the potential energy surface, cis-HOPO(E1) is found to be thermodynamically and kinetically most stable isomer followed by trans-HOPO(E2) and HPO(O)(C2v, E3) at 10.99 and 48.36 kJ/mol higher, respectively. Based on the potential energy surface, only E1 and E3 are thermodynamically stable isomers, and should be experimentally observable. The products cis-HPOO(E5) and frans-HPOO(E6) in the first-step reaction of HP with O2 can isomerize into isomer E1 that has higher stability. The reaction of OH with PO will directly lead to the formation of isomer E1. The computed results are well consistent with the previous experimental studies.展开更多
Structure prediction methods have been widely used as a state-of-the-art tool for structure searches and materials discovery, leading to many theory-driven breakthroughs on discoveries of new materials. These methods ...Structure prediction methods have been widely used as a state-of-the-art tool for structure searches and materials discovery, leading to many theory-driven breakthroughs on discoveries of new materials. These methods generally involve the exploration of the potential energy surfaces of materials through various structure sampling techniques and optimization algorithms in conjunction with quantum mechanical calculations. By taking advantage of the general feature of materials potential energy surface and swarm-intelligence-based global optimization algorithms, we have developed the CALYPSO method for structure prediction, which has been widely used in fields as diverse as computational physics, chemistry, and materials science. In this review, we provide the basic theory of the CALYPSO method, placing particular emphasis on the principles of its various structure dealing methods. We also survey the current challenges faced by structure prediction methods and include an outlook on the future developments of CALYPSO in the conclusions.展开更多
The fast dynamic properties of the surface of metallic glasses(MGs) play a critical role in determining their potential applications. However, due to the significant difference in thermal history between atomic simula...The fast dynamic properties of the surface of metallic glasses(MGs) play a critical role in determining their potential applications. However, due to the significant difference in thermal history between atomic simulation models and laboratory-made samples, the atomic-scale behaviors of the fast surface dynamics of MGs in experiments remain uncertain. Herein, we prepared model MG films with notable variations in thermal stability using a recently developed efficient annealing protocol, and investigated their atomic-scale dynamics systematically. We found that the dynamics of surface atoms remain invariant, whereas the difference in dynamical heterogeneity between surface and interior regions increases with the improvement of thermal stability. This can be associated with the more pronounced correlation between atomic activation energy spectra and depth from the surface in samples with higher thermal stability. In addition, dynamic anisotropy appears for surface atoms, and their transverse dynamics are faster than normal components, which can also be interpreted by activation energy spectra. Our results reveal the presence of strong liquid-like atomic dynamics confined to the surface of laboratory-made MGs, illuminating the underlying mechanisms for surface engineering design, such as cold joining by ultrasonic vibrations and superlattice growth.展开更多
The mechanism of a cycloaddition reaction between singlet methylidenesilene and ethylene has been investigated with MP2/6-31G^＊ and B3LYP/6-31G^＊ methods, including geometry optimization and vibrational analysis for...The mechanism of a cycloaddition reaction between singlet methylidenesilene and ethylene has been investigated with MP2/6-31G^＊ and B3LYP/6-31G^＊ methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies of the involved conformers were calculated by CCSD（T）//MP2/6-31G＊ and CCSD（T）//B3LYP/6-31 G＊ methods, respectively. The results show that the dominant reaction pathway of the cycloaddition reaction is that a complex intermediate is firstly formed between the two reactants through a barrier-free exothermic reaction of 13.3 kJ/mol, and the complex is then isomefized to a four-membered ring product P2,1 via a transition state TS2.1 with a barrier of 32.0 kJ/mol.展开更多
The mechanism of cycloaddition reaction between singlet silylene carbene and acetone has been investigated with CCSD（T）//MP2/6-31G method. From the potential energy profile, it can be predicted that the reaction has...The mechanism of cycloaddition reaction between singlet silylene carbene and acetone has been investigated with CCSD（T）//MP2/6-31G method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. One consists of two steps： （1） the two reactants （R1, R2） firstly form a four-membered ring intermediate （INT4） through a barrier-free exothermic reaction of 585.9 kJ/mol; （2） Then intermediate （INT4） isomerizes to CH3-transfer product （P4.1） via a transition state （TS4.1） with energy barrier of 5.3 kJ/mol. The other is as follows： on the basis of intermediate （INT4） created between R1 and R2, intermediate （INT4） further reacts with acetone （R2） to form the intermediate （INT5） through a barrier-free exothermic reaction of 166.3 kJ/mol; Then, intermediate （INT5） isomerizes to a silicic bis-heterocyclic product （P5） via a transition state （TS5）, for which the barrier is 54.9 kJ/mol. The presented rule of this reaction： the [2＋2] cycloaddition effect between the π orbital of silylene carbene and the π orbital of π-bonded compounds leads to the formation of a four-membered ring intermediate （INT4）; The unsaturated property of C atom from carbene in the four-membered ring intermediate （INT4） results in the generation of CH3-transfer product （P4.1） and silicic bis-heterocyclic compound （P5）.展开更多
An analytic expression of the potential energy surface(PES) of the ground state of the Ne-HF complex is obtained by utilizing nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guiz...An analytic expression of the potential energy surface(PES) of the ground state of the Ne-HF complex is obtained by utilizing nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guizhou Science,2003,21(3):9-13(in Chinese)],which have been computed using the augmented correlation-consistent polarized quadruple zeta basis set aug-cc-pVQZ at the theoretical level of CCSD(T). On the basis of the PES,the partial cross sections(PCSs) at the incident energies of 60,75,100 and 150 meV for collisions between Ne atoms and HF molecules are calculated using the quantum close coupling approach. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic PCSs are discussed in detail. The results show:(1) The long-range attractive well of the EPS makes the significant contribution to the lower excitation PCSs,especially the tail maximum for j = 0→j′ = 1 transitions,whereas no contribution is to the j′≥3 inelastic transitions.(2) The short-range(the repulsive and attractive) interaction makes the significant contri-bution to the lower excitation PCSs,especially the main peak for j = 0→j′ = 1,2. As for the transitions of j′≥3,the short-range interaction plays a key role in the inelastic excitation.(3) Although the positions of the maximums and minimums of the inelastic PCSs are different at the collision energies,they correspond to almost the same impact parameter.展开更多
Topography-induced potential vorticity （PV） banners over a mesoscale topography （Dabie Mountain, hereafter DM） in eastern China, under an idealized dry adiabatic flow, are studied with a mesoscale numerical model,...Topography-induced potential vorticity （PV） banners over a mesoscale topography （Dabie Mountain, hereafter DM） in eastern China, under an idealized dry adiabatic flow, are studied with a mesoscale numerical model, ARPS. PV banners generate over the leeside of the DM with a maximal intensity of ～1.5 PVU, and extend more than 100 km downstream, while the width varies from several to tens of kilometers, which contrasts with the half-width of the peaks along the ridge of the DM. Wave breaking occurs near the leeside surface of the DM, and leads to a strong PV generation. Combining with the PV generation, due to the friction and the flow splitting upstream, the PV is advected downstream, and then forms the PV banners over the DM. The PV banners are sensitive to the model resolution, Coriolis force, friction, subgrid turbulent mixing, stratification, the upstream wind speed and wind direction. The negative PV banners have a more compact connection with the low level turbulent kinetic energy. The PV banners are built up by the baroclinic and barotropic components. The barotropic-associated PV can identify the distribution of the PV banners, while the baroclinic one only has important contributions on the flanks and on the leeside near the topography. PV fluxes are diagnosed to investigate the influence of friction on the PV banners. Similar patterns are found between the total PV flux and the advective PV flux, except near the surface and inside the dipole of the PV banners, where the nonadvective PV flux associated with the friction has a net negative contribution.展开更多
The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the invo...The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD（T）//B3LYP/6-31G＊ method. On the basis of the surface energy profile obtained with CCSD（T）// B3LYP/6-31G＊ method for the cycloaddition reaction between singlet dichloromethylene germylene and ethylene, it can be predicted that the dominant reaction pathway is that an intermediate INT1 is firstly formed between the two reactants through a barrier-free exothermic reaction of 61.7 kJ/mol, and the intermediate INT1 then isomerizes to an active four-membered ring product P2.1 via a transition state TS2, an intermediate INT2 and a transition state TS2.1, in which energy barriers are 57.7 and 42.2 kJ/mol, respectively.展开更多
文摘在昆明西山国家森林公园地盘松林连续分布区内设置样地,并将样地内的地表凋落物分成枯枝、凋落物上层和凋落物下层3层,通过外业调查采集样品,在实验室测定载量、热值等相关燃烧能量参数,以单位面积热量为关键指标研究地盘松林地表凋落物的潜在能量。结果表明,在地盘松林地表凋落物中,凋落物上层、下层和枯枝的单位面积热量最大值差异不大,分别为51 866.3 k J/m2、48 942.13 k J/m2和42 611.53 k J/m2;平均值的差异也不大,分别为38 688.5 k J/m2、39 716.63 k J/m2和25 796.23 k J/m2。但最低值的差异却非常明显,凋落物上层的为25 510.8 k J/m2,枯枝的为8 980.93 k J/m2,凋落物下层的为30 491.1 k J/m2。
基金Supported by the National Natural Science Foundation of China under Grant No 10676025, the Natural Science Foundation of the Anhui Higher Education Institutions of China, and the Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20050610010.
文摘The close-coupling method is utilized to calculate partial cross sections for elastic and inelastic scattering of He atoms with HX （X=F, Cl, Br） molecule based on the CCSD （T） potential energy surfaces obtained in the previous research. The calculation is performed at the incident energy of 200 me V. The rationality of our results has been confirmed by comparison with the available theoretical results. The tendency of the elastic and inelastic rotational excitation partial wave cross sections varying with the reduced mass of the three systems is obtained.
基金supported by the National Key R&D Program of China(Grant No.2018YFA0404402)the National Natural Science Foundation of China(Grant Nos.11525524,11621131001,11647601,11747601,and 11711540016)+3 种基金the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.QYZDB-SSWSYS013)the Key Research Program of Chinese Academy of Sciences(Grant No.XDPB09-02)the Inter-Governmental S&T Coorperation Project between China and Croatiathe IAEA Coordinated Research Project “F41033”
文摘We study the ground state properties, potential energy curves and potential energy surfaces of the superheavy nucleus270 Hs by using the multidimensionally-constrained relativistic mean-field model with the effective interaction PC-PK1. The binding energy,size and shape as well as single particle shell structure corresponding to the ground state of this nucleus are obtained.270 Hs is well deformed and exhibits deformed doubly magic feature in the single neutron and proton level schemes. One-dimensional potential energy curves and two-dimensional potential energy surfaces are calculated for270 Hs with various spatial symmetries imposed. We investigate in detail the effects of the reflection asymmetric and triaxial distortions on the fission barrier and fission path of270 Hs. When the axial symmetry is imposed, the reflection symmetric and reflection asymmetric fission barriers both show a double-hump structure and the former is higher. However, when triaxial shapes are allowed the reflection symmetric barrier is lowered very much and then the reflection symmetric fission path becomes favorable.
基金This work was supported by the National Natural Science Foundation of China (No. 20341005), Natural Science Foundation of Shanxi Province (No. 20011015) and the Foundation for University Key Teachers by the Ministry of Education
文摘The structures of closo-hedral cluster (HAlNH)12 and endohedral complexes X@(HAlNH)12 (X = He, Ne, Ar, Kr) have been studied by using density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natural bond orbital (NBO), vibrational frequency, energetic parameters, magnetic shielding constants and nucleus independent chemical shifts (NICS) were discussed. The potential surface of guest X shifting from the cage center to a face of six- membered ring was calculated at the same level. The exit transition state was demonstrated with IRC calculations. It is found that X@(HAlNH)12 complexes are dynamically stable, and Ne@(HAlNH)12 is more energetically favorable than the other complexes in thermodynamics.
文摘When surface potential of the particles,ψ ,is high,sinh y can be approximated by≈ ey/2 in the nonlinear Poisson Boltzmann equation.Thus,we present a simple method of calculating the interaction force and energy per unit area between two dissimilar plates with high potentials at constant surface potential.These formulae could be applicable to the case of repulsive case,in which the derivative of y must vanish at an interior point,and a minimum ymin=u always exists.A turning point at～κ h≈ 2(π－ 1)e－ y1/2 for the repulsion or attraction between dissimilar planar surfaces.These formulae are divergent atκ h∞ ,and zero point atκ h≈ 2π .This means that they can only be used atκ h < 2π and accurate location is atκ h≤ 4. Agreement of the approximation for force,Eq.（ 13） ,is good with the exact numerical values of the interaction of dissimilar plates given by Devereux [6] for high surface potentials.For y1≥ 5κ h≤ 3.0 the relative errors of Eq.(13) are less than 5％ ,and forκ h≤ 3.5 relative errors are less than 10％ .For the interaction energy,Eq.(15),the applicable range extends toκ h=4.0.Beyond this range the error increases rapidly.The higher surface potential is the better the precision of Eq.（ 13） and Eq.( 15).The condition of the strong interaction has been satisfied.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.20301006,20271019)the Science Foundation for Distinguished Young Scholar of Heilongjiang Province(2003).
文摘Some stationary points on the potential energy surface of [Si, N, N, P] system were located at the B3LYP/6-311G(d) and QCISD(t)/6-311+G(2df)(single-point) levels of theory, while the isomerization, structures, and stability of these obtained isomers were suggested. The computed results indicate that only four-membered ring isomer SiNPN(E1, 2A'), which possesses butterfly-like structure and Si-P cross bonding, is kinetically stable in all optimized isomers. Other isomers may be considered as kinetically unstable towards isomerization or dissociation because of the corresponding smaller reaction barriers. Furthermore, the present paper also proposes electronic and geometric structures, vibrational frequencies and the corresponding vibrational modes, dipole moments, and rotational constants of isomer E1. To make use of the computed results, we can clearly know that the reaction pathway via an intermediate E3 (SiNPN) is the most favorable channel producing isomer E1 from fragments SiN(2Π) and PN (1Σ), which have been well characterized in space, and thus, isomer E1 can be considered as a candidate for interstellar observation. The reaction enthalpy of SiN(2Π) + PN(1Σ)→ E1 and the standard enthalpy of formation of isomer E1 are 215.25 and 457.99 kJ/mol, respectively, at 298.15 K. Keywords potential energy surface - [Si,N,N,P] system - isomerization - kinetic stability
基金This work was supported by the National Natural Science Foundation of China (Grant Nos.29892168, 20171015 and 20171016) Science Foundation for Excellent Youths of Heilongjiang University (2002) the Natural Science Foundation of Heilongjiang Provinc
文摘The potential energy surface of HPO2 system including eight isomers and twelve transition states is predicated at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df,2p)(single-point) levels of theory. On the potential energy surface, cis-HOPO(E1) is found to be thermodynamically and kinetically most stable isomer followed by trans-HOPO(E2) and HPO(O)(C2v, E3) at 10.99 and 48.36 kJ/mol higher, respectively. Based on the potential energy surface, only E1 and E3 are thermodynamically stable isomers, and should be experimentally observable. The products cis-HPOO(E5) and frans-HPOO(E6) in the first-step reaction of HP with O2 can isomerize into isomer E1 that has higher stability. The reaction of OH with PO will directly lead to the formation of isomer E1. The computed results are well consistent with the previous experimental studies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11534003 and 11604117)the National Key Research and Development Program of China(Grant No.2016YFB0201201)+1 种基金the Program for JLU Science and Technology Innovative Research Team(JLUSTIRT)of Chinathe Science Challenge Project of China(Grant No.TZ2016001)
文摘Structure prediction methods have been widely used as a state-of-the-art tool for structure searches and materials discovery, leading to many theory-driven breakthroughs on discoveries of new materials. These methods generally involve the exploration of the potential energy surfaces of materials through various structure sampling techniques and optimization algorithms in conjunction with quantum mechanical calculations. By taking advantage of the general feature of materials potential energy surface and swarm-intelligence-based global optimization algorithms, we have developed the CALYPSO method for structure prediction, which has been widely used in fields as diverse as computational physics, chemistry, and materials science. In this review, we provide the basic theory of the CALYPSO method, placing particular emphasis on the principles of its various structure dealing methods. We also survey the current challenges faced by structure prediction methods and include an outlook on the future developments of CALYPSO in the conclusions.
基金sponsored by the National Natural Science Foundation of China (Grant No. 52101201)supported by the National Natural Science Foundation of China (Grant No.T2325004)+2 种基金sponsored by the National Natural Science Foundation of China(Grant No. 51801046)the Natural Science Foundation of Chongqing,China (Grant No. cstc2021jcyj-msxm X0369)the Science Fund for Scientific and Technological Innovation Team of Shaanxi Province (Grant No. 2021TD-14)。
文摘The fast dynamic properties of the surface of metallic glasses(MGs) play a critical role in determining their potential applications. However, due to the significant difference in thermal history between atomic simulation models and laboratory-made samples, the atomic-scale behaviors of the fast surface dynamics of MGs in experiments remain uncertain. Herein, we prepared model MG films with notable variations in thermal stability using a recently developed efficient annealing protocol, and investigated their atomic-scale dynamics systematically. We found that the dynamics of surface atoms remain invariant, whereas the difference in dynamical heterogeneity between surface and interior regions increases with the improvement of thermal stability. This can be associated with the more pronounced correlation between atomic activation energy spectra and depth from the surface in samples with higher thermal stability. In addition, dynamic anisotropy appears for surface atoms, and their transverse dynamics are faster than normal components, which can also be interpreted by activation energy spectra. Our results reveal the presence of strong liquid-like atomic dynamics confined to the surface of laboratory-made MGs, illuminating the underlying mechanisms for surface engineering design, such as cold joining by ultrasonic vibrations and superlattice growth.
基金Project supported by the Natural Science Foundation of Shandong Province of China （No. Y2002B07）.
文摘The mechanism of a cycloaddition reaction between singlet methylidenesilene and ethylene has been investigated with MP2/6-31G^＊ and B3LYP/6-31G^＊ methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies of the involved conformers were calculated by CCSD（T）//MP2/6-31G＊ and CCSD（T）//B3LYP/6-31 G＊ methods, respectively. The results show that the dominant reaction pathway of the cycloaddition reaction is that a complex intermediate is firstly formed between the two reactants through a barrier-free exothermic reaction of 13.3 kJ/mol, and the complex is then isomefized to a four-membered ring product P2,1 via a transition state TS2.1 with a barrier of 32.0 kJ/mol.
文摘The mechanism of cycloaddition reaction between singlet silylene carbene and acetone has been investigated with CCSD（T）//MP2/6-31G method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. One consists of two steps： （1） the two reactants （R1, R2） firstly form a four-membered ring intermediate （INT4） through a barrier-free exothermic reaction of 585.9 kJ/mol; （2） Then intermediate （INT4） isomerizes to CH3-transfer product （P4.1） via a transition state （TS4.1） with energy barrier of 5.3 kJ/mol. The other is as follows： on the basis of intermediate （INT4） created between R1 and R2, intermediate （INT4） further reacts with acetone （R2） to form the intermediate （INT5） through a barrier-free exothermic reaction of 166.3 kJ/mol; Then, intermediate （INT5） isomerizes to a silicic bis-heterocyclic product （P5） via a transition state （TS5）, for which the barrier is 54.9 kJ/mol. The presented rule of this reaction： the [2＋2] cycloaddition effect between the π orbital of silylene carbene and the π orbital of π-bonded compounds leads to the formation of a four-membered ring intermediate （INT4）; The unsaturated property of C atom from carbene in the four-membered ring intermediate （INT4） results in the generation of CH3-transfer product （P4.1） and silicic bis-heterocyclic compound （P5）.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10676025 and 10574096)
文摘An analytic expression of the potential energy surface(PES) of the ground state of the Ne-HF complex is obtained by utilizing nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guizhou Science,2003,21(3):9-13(in Chinese)],which have been computed using the augmented correlation-consistent polarized quadruple zeta basis set aug-cc-pVQZ at the theoretical level of CCSD(T). On the basis of the PES,the partial cross sections(PCSs) at the incident energies of 60,75,100 and 150 meV for collisions between Ne atoms and HF molecules are calculated using the quantum close coupling approach. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic PCSs are discussed in detail. The results show:(1) The long-range attractive well of the EPS makes the significant contribution to the lower excitation PCSs,especially the tail maximum for j = 0→j′ = 1 transitions,whereas no contribution is to the j′≥3 inelastic transitions.(2) The short-range(the repulsive and attractive) interaction makes the significant contri-bution to the lower excitation PCSs,especially the main peak for j = 0→j′ = 1,2. As for the transitions of j′≥3,the short-range interaction plays a key role in the inelastic excitation.(3) Although the positions of the maximums and minimums of the inelastic PCSs are different at the collision energies,they correspond to almost the same impact parameter.
基金supported bythe National Key Scientific and Technological Project2006BAC02B03, 2004CB418300, GYHY2000706033 under the FANEDD 200325the Specialized Research Fund for the Doctoral Program of Higher Education (No.20080284019)National Natural Science Foundation of China under Grant Nos. 40705019, 40325014 and 40333031
文摘Topography-induced potential vorticity （PV） banners over a mesoscale topography （Dabie Mountain, hereafter DM） in eastern China, under an idealized dry adiabatic flow, are studied with a mesoscale numerical model, ARPS. PV banners generate over the leeside of the DM with a maximal intensity of ～1.5 PVU, and extend more than 100 km downstream, while the width varies from several to tens of kilometers, which contrasts with the half-width of the peaks along the ridge of the DM. Wave breaking occurs near the leeside surface of the DM, and leads to a strong PV generation. Combining with the PV generation, due to the friction and the flow splitting upstream, the PV is advected downstream, and then forms the PV banners over the DM. The PV banners are sensitive to the model resolution, Coriolis force, friction, subgrid turbulent mixing, stratification, the upstream wind speed and wind direction. The negative PV banners have a more compact connection with the low level turbulent kinetic energy. The PV banners are built up by the baroclinic and barotropic components. The barotropic-associated PV can identify the distribution of the PV banners, while the baroclinic one only has important contributions on the flanks and on the leeside near the topography. PV fluxes are diagnosed to investigate the influence of friction on the PV banners. Similar patterns are found between the total PV flux and the advective PV flux, except near the surface and inside the dipole of the PV banners, where the nonadvective PV flux associated with the friction has a net negative contribution.
基金Project supported by the Natural Science Foundation of Shandong Province of China （No. Y2002B07）.
文摘The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD（T）//B3LYP/6-31G＊ method. On the basis of the surface energy profile obtained with CCSD（T）// B3LYP/6-31G＊ method for the cycloaddition reaction between singlet dichloromethylene germylene and ethylene, it can be predicted that the dominant reaction pathway is that an intermediate INT1 is firstly formed between the two reactants through a barrier-free exothermic reaction of 61.7 kJ/mol, and the intermediate INT1 then isomerizes to an active four-membered ring product P2.1 via a transition state TS2, an intermediate INT2 and a transition state TS2.1, in which energy barriers are 57.7 and 42.2 kJ/mol, respectively.
