The effects of pre-equilibrium emission and secondary decay on the determination of freeze-out volume at intermediate energies

The effects of pre-equilibrium emission and secondary decay on the determination of the freeze-out volume are investigated using the isospin-dependent quantum molecular dynamics model accompanied by the statistical decay model GEMINI. Small-mass projectiles and large-mass targets with central collisions are studied at intermediate energies. It is revealed that the proton yields of pre-equilibrium emission are smaller than those of secondary decay. However, the determination of the freeze-out volume from the proton yields is more easily affected by pre-equilibrium emission. Moreover, the percentage of proton yields in the freeze-out stage is found to be approximately 50%.     

Hybrid cobalt hydroxyoxalate material containing 3D Co-O-Co connectivity and showing ferrimagnetic ordering

A hybrid material constructed of 3/19 site-modified Brucite-like cobalt hydroxide and cobalt-oxalate, two types of new layered structural motifs, has been synthesized that shows rare 3D Co-O-Co connectivity and ferrimagnetic ordering.     

The generalized block-localized wavefunction method: a case study on the conformational preference and C-O rotational barrier of formic acid

A Lewis structure corresponding to the most stable electron-localized state is often used as a reference for the measure of electron delocalization effect in the valence bond (VB) theory. As the simplest variant of ab initio VB theory, the generalized block-localized wavefunction (BLW) method defines the wavefunction for an electron-localized state with block-localized orbitals without the orthogonalization constraint on different blocks. The validity of the method can be critically examined with experimental evidences. Here the BLW method has been applied to the investigation of the roles of both the π conjugation and σ hyperconjugation effects in the conformational preference of formic acid for the trans (Z) conformer over the cis (E) conformer. On one hand, our computations showed that the deactivation of the π conjugation or σ hyperconjugation has little impact on the Z-E energy gap, thus neither is decisive and instead the local dipole-dipole electrostatic interaction between the carbonyl and hydroxyl groups is the key factor determining the Z-E energy gap. On the other hand, the present study supported the conventional view that π conjugation is largely responsible for the C-O rotation barrier in formic acid, though the existence of hyperconjugative interactions in the perpendicular structure lowers the barrier considerably.     

(XY)12(X=B,Al;Y=P)团簇的结构与稳定性

采用B3LYP／6031G*方法,对(XY)12(X=B,Al;Y=P)笼状团簇的同分异构体进行优化,筛选出能量最低的构型．讨论它们的几何构型、HOMO-LUMO能隙、生成焓、核独立化学位移(NICS)和自由能．得到(BP)12和(AlP)12团簇的最稳定构型均为具有Th对称性的四、六元环组成的笼,亚稳态结构中含有五元环。     

3d系列 (TM)4 团簇的结构和磁性

基于第一性原理，在密度泛函理论下，用局域自旋密度近似(LSDA)和广义梯度近似(GGA)对(TM)₄团簇的所有几何构型进行优化、能量、频率和磁性计算.确定出3d系列(TM)₄团簇的基态构型，对其磁性、结合能和平均原子间距作了系统的研究，得出在3d系列(TM)₄团簇中，Mn₄的局域磁矩最大，V₄的局域磁矩最小，并且除Cr₄在LSDA和GGA均为反铁磁性耦合及GGA下的V_{关键词： 4}团簇')" href="#">(TM)₄团簇 基态构型 结合能 局域磁矩 平均原子间距     

Inversed stability order in Keggin polyoxothiometalate isomers: a DFT study of 12-electron reduced alpha, beta, gamma, delta, and epsilon [(MoO4)Mo12O12S12(OH)12]2- anions

Density functional theory calculations have been carried out to investigate 12-electron reduced alpha, beta, gamma, delta, and epsilon Keggin-like [(MoO4)Mo12O12S12(OH)12]2- polyoxothiometalates (POTMs), which show that the stability order is alpha < beta < gamma < delta < epsilon that is perfectly inverse to the well-known trend of the classical Keggin polyoxometalates. Energy decomposition analysis reveals that the enhanced stabilities of gamma, delta, and epsilon isomers originate the favorable arrangements of their Mo12O12S12(OH)12 shell, in which the edge-sharing [MoV2(mu-S)2O2] fragment plays a fundamental role in stabilizing the overall structure. Both frontier orbital analysis and Mayer indexes exhibit that a Mo-Mo single bond is formed inside the [MoV2(mu-S)2O2] fragment, which leads to the localization of the two reduced electrons. As compared with experimentally discovered cyclic [(C9H3O6)@Mo12O12S12(OH)12]3-, all Keggin POTM structures are less stable due to their disfavored cage framework and the disadvantageous host-guest interaction. However, the epsilon-type Keggin POTM that has the largest similarity to the cyclic species is possibly available in the presence of appropriate templates.     

Theoretical Analysis of the Mechanism of Cationic Pd(Ⅱ)-catalyzed Fujiwara-Moritani Reaction

A systematic theoretical investigation has been studied on Fujiwara-Moritani reaction between 3-methoxyacetanilide with n-butyl acrylate by means of density functional theory(DFT) calculations when two types of Pd(Ⅱ) catalysts are employed. In [Pd(MeCN)_4](BF_4)_2 catalytic cycle, a 1,4-benzoquinone(BQ)-induced C-H activation of trans-(MeCN)_2Pd(BQ)~(2+) with 3-methoxyacetanilide occurs as the first step to give DC-4_(MeCN), facilitating the insertion of n-butyl acrylate and β-hydride elimination, followed by recycling of catalyst through hydrogen abstraction of monocationic BQ fragment. In Pd(OAc)_2 catalytic cycle, it is proposed that the most favored reaction pathway should proceed in dicationic mechanism involving a BQ-assisted hydrogen transfer for C-H activation by Pd active catalyst(HOAc)_2Pd(BQ)~(2+) to generate DC-4_(HOAc), promoting acrylate insertion and β-hydride elimination, followed by the regeneration of catalyst to give the final product. The calculations indicate that the rate-determining step in [Pd(MeCN)_4](BF_4)_2 catalytic system is the acrylate insertion, while it is the regeneration of catalyst in the Pd(OAc)_2 catalytic system. In particular, the roles of BQ and ligand effects have also been investigated.     

X@(HAINH)_(12)和X(HAINH)_(12)(X=F~-,Cl~-,Br~-,O~(2-),S~(2-),Se~(2-))复合物的结构和稳定性

用DFT的B3LYP方法在6-31G(d)基组的水平上,对闭式多面体簇合物(HA1NH)12及其内含式X@(HA1NH)12外接式X(HA1NH)12(X=F-,Cl-,Br-,O2-,S2-,Se2-)复合物的结构进行了构型优化和能量计算,并讨论了几何构型、自然键轨道(NBO)、振动频率、能量参数及NMR数据与结构的关系,最后得到复合物结构的稳定性信息,具有Th对称性的X@(HA1NH)12(X=F-,Cl-,Br-,S2-,Se2-)复合物和具有C3对称性的O2-@(HA1NH)12复合物为内含式的基态结构,从能量角度分析,内含式复合物比外接式复合物的结构稳定.     

X@(HAlNH)12和X(HAlNH)12 (X＝F－, Cl－, Br－, O2－, S2－, Se2－)复合物的结构和稳定性

用DFT的B3LYP方法在6-31G(d)基组的水平上, 对闭式多面体簇合物(HAlNH)₁₂及其内含式X@(HAlNH)₁₂和外接式X(HAlNH)₁₂ (X＝F^－, Cl^－, Br^－, O^2－, S^2－, Se^2－)复合物的结构进行了构型优化和能量计算, 并讨论了几何构型、自然键轨道(NBO)、振动频率、能量参数及NMR数据与结构的关系, 最后得到复合物结构的稳定性信息, 具有T_h对称性的X@(HAlNH)₁₂ (X＝F^－, Cl^－, Br^－, S^2－, Se^2－)复合物和具有C₃对称性的O^2－@(HAlNH)₁₂复合物为内含式的基态结构, 从能量角度分析, 内含式复合物比外接式复合物的结构稳定.