计算分子二阶超极化率的基组选择

设计和使用了扩展的6-31G,D95, ANO,aug-cc-pVDZ基组以及Hypol基组,用各种相关能级别的方法SCF,MP2,MP3,MP4D,MP4DQ,MP4SDQ,MP4, CCSD,CCSD(T),计算了H2O,CO,HF,H2,N2等分子的二阶超极化率.分别以4-aug-cc-pVTZ基组在不同方法下的二阶超极化率结果,和CCSD(T)/4-aug-cc-pVTZ水平上的结果作为标准,求得各水平计算相对应的平均相对偏差.结果发现:MP2/aug-cc- pVDZ+是计算二阶超极化率最优的水平.综合讨论认为:可在MP2/aug-cc-pVDZ+水平上计算分子的二阶超极化率,其结果是可靠的.而且如果同时要计算分子极化率和一阶超极化率,其结果也是可靠的.     

Alkali and alkaline earth metal compounds: core—valence basis sets and importance of subvalence correlation

Core-valence basis sets for the alkali and alkaline earth metals Li, Be, Na, Mg, K, and Ca are proposed. The basis sets are validated by calculating spectroscopic constants of a variety of diatomic molecules involving these elements. Neglect of (3s, 3p) correlation in K and Ca compounds will lead to erratic results at best, and chemically nonsensical ones if chalcogens or halogens are present. The addition of low-exponent p functions to the K and Ca basis sets is essential for the smooth convergence of molecular properties. Inclusion of inner-shell correlation is important for accurate spectroscopic constants and binding energies of all the compounds. In basis set extrapolation/convergence calculations, the explicit inclusion of alkali and alkaline earth metal subvalence correlation at all steps is essential for K and Ca, strongly recommended for Na, and optional for Li and Mg, while in Be compounds an additive treatment in a separate ‘core correlation’ step is probably sufficient. Consideration of (ls) inner-shell correlation energy in first-row elements requires the inclusion of (2s, 2p) ‘deep core’ correlation energy in K and Ca for consistency. The latter requires special CCVnZ ‘deep core correlation’ basis sets. For compounds involving Ca bound to electronegative elements, additional d functions in the basis set are strongly recommended. For optimal basis set convergence in such cases, we suggest the sequence CV(D + 3d)Z, CV(T + 2d)Z, CV(Q + d)Z, and CV5Z on calcium.     

OH分子基态和第一激发态的势能函数

采用多参考组态作用(MRCI)方法和aug-cc-pVTZ,aug-cc-pVQZ,cc-pV5Z,6-311++g(d,p)和6-311++g(3df,3pd)几个不同基组对OH分子的基态(X²Π)和第一激发态(A²Σ⁺)的势能曲线进行计算.选用Murrell-Sorbie势能函数对曲线进行拟合,利用拟合的参数值计算出力常数和光谱数据.结果表明计算值与实验值吻合较好.     

Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

Background  

In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types.     

采用振速测量的改进统计最优近场声全息方法

针对常规统计最优近场声全息在空间多源声场重建过程中所需波函数项数多、重建精度不理想的问题,本文提出了一种基于振速测量的改进统计最优近场声全息算法。与常规算法不同,改进算法主要根据声源特点选取合适的波函数组合来计算声场传递矩阵。通过数值仿真初步验证了该方法的准确性和有效性,并与常规算法进行了详细的对比分析。仿真结果表明,改进算法重建精度高,随频率的变化相对误差波动较小,且随着频率的增大相对误差有逐渐减小的趋势;此外,不同的波函数组合,重建效果差异很大,当选取的波函数与声源共形且数量一致时重建效果最好。     

New basis sets for the evaluation of the CO–Ne van der Waals complex interaction induced electric dipole moment and polarizability surfaces

Using the coupled cluster singles and doubles method together with the recently developed LPol-n (n?=?ds, dl, fs, fl), the aug-pc-2, the SVPD, the TZVPD and Dunning's x-aug-cc-pVXZ basis sets, we calculate the interaction induced electric dipole moment and polarizability of the CO–Ne van der Waals complex. We consider the effect of extending the bases with different sets of mid-bond functions, and after a systematic basis set study carried out at a representative set of intermolecular geometries, we select the aug-cc-pVTZ, the aug-pc-2, the LPol-fs and the TZVPD bases with a set of 3s3p2d1f1g mid-bond functions placed in the middle of the van der Waals bond for the evaluation of the whole interaction induced property surfaces. After having determined the optimal parameters of appropriate analytical functions fitting the interaction induced properties, the resulting surfaces are used in semiclassical calculations of the dielectric and refractivity second virial coefficients of the system. All through this study the results obtained with Dunning's basis set hierarchy and reported in Phys. Chem. Chem. Phys., 11, 9871 (2009) are taken as reference.     

Visualization of deficiencies in approximate molecular wave functions: the local orbital energy function for the matrix Hartree—Fock model

The local orbital energy function is used to assess the quality of approximate Hartree-Fock orbitals obtained by invoking the algebraic approximation and using a finite basis set expansion. Systematic sequences of distributed universal even-tempered basis sets of spherical-harmonic Gaussian-type functions are used to generate orbitals for which the corresponding total Hartree-Fock energy approaches the 1 μE_h level of accuracy. A pilot study of the behaviour of the local energy function is made for the hydrogenic atom described by a sequence of even-tempered Gaussian basis sets. The results of prototype calculations for the Hartree-Fock ground state of the BF molecule at its equilibrium geometry are presented. Sequences of calculations which use atom-centred basis sets are investigated as well as sequences which also include bond centred functions. The effects of the bond centred functions on the local orbital energy function are analysed. The local orbital energy function is seen as a measure of the quality of calculations carried out within the matrix Hartree-Fock approximation which can be employed in cases where the corresponding finite difference Hartree-Fock results are not available.     

Basis set limit binding energies of hydrogen bonded clusters

The utility of the recently developed extrapolation method to estimate the binding energies of weakly bound clusters at the basis set limit exploiting the similar basis set convergence behaviour of correlation energies of the monomer and cluster in correlated calculations (J. chem. Phys., 116, 5389 (2002)) was tested for small to medium (HF)_n and (H₂O)_n (n = 2–5) clusters using various correlation consistent cc-pVXZ (X= D,T,Q,5) basis sets containing different numbers of diffuse functions and 6–31G type basis sets at the MP2 and CCSD(T) level for which accurate basis set limits are available for comparison. It is shown that the basis set limit binding energies estimated by this extrapolation method with modest size of basis sets (cc-pVDZ/cc-pVTZ or 6–3 1 G(d,p)/6-3 IG(2df,2pd)) are much closer to the exact basis set limits than the estimates by commonly used X ^?3 extrapolation or counterpoise corrected binding energies, signifying the importance of this extrapolation method for the study of large weakly bound clusters. It is also shown that the inclusion of appropriate diffuse functions in the basis sets can significantly improve the accuracy of the estimated basis set limits by this extrapolation method. For (HF)_n clusters the MP2 and CCSD(T) basis set limits estimated by this extrapolation method with aug-cc-pVDZ and aug-cc-pVTZ basis sets are 18.4 (18.5) and 18.9 (18.9) for the dimer, 61.8 (62) and 63.2 (63) for the trimer, 113.5 and 114.7 (116) for the tetramer, and 155.2 and 156.3 (158) for the pentamer, respectively, with the values in parentheses representing the apparent basis set limits, with the numbers in units of kJ mol^?1. The corresponding results for (H₂O)_n clusters are 20.5 (20.5) and 20.6 (20.7) for (H₂O)₂, and 60.5 (61) and 60.1 (60) for (H₂O)₃, respectively.     

Glutamate-induced glutamate release: a proposed mechanism for calcium bursting in astrocytes

Here we present a new model for the generation of complex calcium-bursting patterns in astrocytes, a type of brain cell recently implicated in a variety of neural functions including memory formation. The model involves two positive feedback processes, in which the key feedback species are calcium ion and glutamate. The latter is the most abundant excitatory neurotransmitter in the brain and has been shown to be involved in bidirectional communication between astrocytes and nearby neurons. The glutamate feedback process considered here is shown to be critical for the generation of complex bursting oscillations in the astrocytes and to, perhaps, code for information which may be passed from neuron to neuron via the astrocyte. These processes may be involved in memory storage and formation as well as in mechanisms which lead to dynamical diseases such as epilepsy.     

Be-CO体系的相互作用势和光谱预测

采用单双迭代（包括非迭代三重激发）耦合簇CCSD （T）理论方法和大基组,计算Be-CO体系的相互作用势,得到该体系势能面的解析表达.发现在R_e=8.29a₀和θ_e=115.42°处存在的一个全局极小势阱,阱深-69.21 cm^-1,势能面呈现较弱的各项异性.根据势能面,计算了体系的束缚态能级和其光谱常数.     

Ne-BeH体系的相互作用势和能级结构的理论研究

本文对Ne-BeH体系采用单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法,对Be , H 和 Ne原子采用aug-cc-pVQZ基组和3s3p2d1f1g中心键函数.利用非线性最小二乘法拟合该理论水平下的相互作用能,得到了Ne-BeH弱相互作用体系在冻结BeH键长情况下的二维的全程势能面,在 和 处存在一全局最小值-34.43607 .利用该势能面,计算了Ne-BeH体系的J=0-9的能级结构.以期对Ne-BeH的相关的实验和理论研究提供必要的参考和借鉴.     

Ne-BeH体系的相互作用势和能级结构的理论研究

本文对Ne-BeH体系采用单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法,对Be , H 和 Ne原子采用aug-cc-pVQZ基组和3s3p2d1f1g中心键函数.利用非线性最小二乘法拟合该理论水平下的相互作用能,得到了Ne-BeH弱相互作用体系在冻结BeH键长情况下的二维的全程势能面,在 和 处存在一全局最小值-34.43607 .利用该势能面,计算了Ne-BeH体系的J=0-9的能级结构.以期对Ne-BeH的相关的实验和理论研究提供必要的参考和借鉴.     

Berechnung der isotropen Kopplungskonstanten für die Wechselwirkung zwischen den Kernspins inHD

The coupling constant is calculated by using several basis sets of Gaussian functions differing in size and parameters. For the first time the result of 42.40 cps is in very satisfactory agreement with experiment (42.7?+0.5 cps). The calculations justify our conclusions that 1^st one has to determine classes of excited states which are complete respective to the chosen basis set, 2^d the restriction to the class of singly excited states is adequate and 3^d correlation effects must be included but a perturbational approach is sufficient. These restrictions are essential for handling large basis sets which makes our method transferable to larger molecules.     

LaF分子结构与基态X1Σ+势能曲线研究

用能量一致相对论有效核芯势和含极化函数 4f2g和弥散函数 1s1p1d的价基组 ,在各种计算水平上计算了LaF分子结构、振动频率和离解能 .根据原子分子反应静力学原理导出LaF分子基态可能的电子状态和离解极限 ,用密度泛函理论中的B3LYP方法计算了基态X1Σ+ 势能曲线 ,拟合得到了Murrell Sorbie解析势能函数及其在平衡位置附近的Dunham展开式 ,由此计算的振转常数和实验光谱数据完全吻合 .得到的解析势能函数可用于计算振转光谱精细跃迁结构和原子分子碰撞反应动力学过程 ,具有重要的实用意义 . The equilibrium geometry, harmonic frequency and dissociation energy of the molecule LaF have been calculated on several kinds of computation levels with energy-consistent relativistic effective core potentials and valence basis sets including polarization functions 4f2g and diffuse functions 1s1p1d. The possible electronic state and its reasonable dissociation limit for the ground state of LaF are determined based on Atomic and Molecular Reaction Statics(AMRS). The potential energy curve scan for...     

Observation of pair absorption in calcium

Pair absorption has been observed in calcium using broad band absorption. The absorption peaks at the sum energy of the (4s4p) ¹P° and (4s3d) ¹D atomic states. A cross section of 1.3 × 10^-22 (P/A) cm² is measured corresponding to a reduced absorption coefficient of 1.3 × 10^-35 cm⁵. An error in earlier calculations predicting the reduced absorption coefficient for pair absorption in barium is noted. Simple scaling laws, our experimental results, and the assumption that the barium process is dominated by the resonant dipole-dipole interaction are used to deduce an upper limit for the calcium (4s3d) ¹D→(4s4p) ¹P° oscillator strength of 6.5 × 10^-4.     

Gaussian basis sets of triple and quadruple zeta valence quality for correlated wave functions

Contracted basis sets of triple and quadruple zeta (TZ and QZ, respectively) valence quality for the atoms from H to Ar are presented. They have been determined from fully-optimized basis sets of primitive Gaussian-type functions generated in atomic Hartree–Fock (HF) calculations. Sets of Gaussian polarization functions optimized at the Møller–Plesset second-order (MP2) level were added to the TZ and QZ basis sets. This extends earlier work on segmented contracted double zeta valence basis sets. The performance of the basis sets are assessed in molecular HF and MP2 calculations for a sample of diatomic molecules by a comparison of energies, dissociation energies, and dipole moments with results obtained numerically or using basis sets reported in the literature. By fitting the directly calculated values through two extrapolation schemes, estimates of the complete basis set limit for second order correlation energy have been obtained. In addition, results for MP2-R12/A calculations to establish the basis set convergence for the standard calculations are also presented.     

间苯二酚-甲醛气凝胶单体分子结构研究

本文用B3LYP密度泛函方法,在6- 311G、6-311++G、6-311G* *和6-311++G* *基组水平上,全空间优化了间苯二酚和甲醛单体分子的几何结构,得到间苯二酚和甲醛分子稳定结构均为平面构型,在不同基组下计算的结果表明极化函数对间苯二酚分子结构有明显影响,而扩散函数对其影响不大;并在此基础上全空间优化了单元/二元羟甲基间苯二酚的平衡构型,得到单元/二元羟甲基间苯二酚单体各分别存在四种异构体,计算了间苯二酚和羟甲基间苯二酚的电荷分布,分析了亚稳态向最稳态过渡的趋势.     

Gaussian-type functions for the 3d Rydberg and 3d correlation orbitals in B to Ne and Al to Ar

Gaussian-type basis sets for the 3d Rydberg orbitals and 3d correlation orbitals are developed for the first- and second-row main group elements. The numbers of the Gaussian-type functions (GTFs) used for the 3d orbitals are 1–3 for the former elements and 1–4 for the latter elements. The 3d Rydberg orbitals for the first-row main group elements are close to the hydrogen (H) 3d orbitals, but those of the second-row main group elements are very different from H 3d except for Al. A two d or three d GTF set suffices to model the first-row main group elements, but at least four d GTFs are necessary for the second-row main group elements. The Rydberg GTF orbitals, consisting of three GTFs, are converted into correlating orbitals by introducing a single scaling factor. The correlation energies (CEs) calculated using these correlating orbitals cover 99.4–100% of those calculated using Dunning's three primitive GTFs for the first-row main group elements, and 94.9–99.7% of the CEs of Woon and Dunning's d's for the second-row main group elements. The resulting correlating 3d orbitals were tested by picking out F₂ and Cl₂, yielding spectroscopic constants close to or more accurate than those calculated by Dunning's 3d orbitals and Woon and Dunning's 3d orbitals.