NaB2和Na2B的结构与解析势能函数

使用Gaussian03程序包,采用单双取代耦合簇(CCSD)方法,选择基组6-311+g(2df)、6-311++g(3df,3pd)分别对B2及NaB和Na2分子的基态进行优化计算,运用最小二乘法拟合得到B2、NaB和Na2分子势能函数,给出与实验值符合很好的光谱常数;选择6-31++g（3df,3pd）基组,对NaB2和Na2B分子的结构进行优化计算.在此基础上,采用多体项展式法,得到NaB2和Na2B分子基态解析势能函数.势能面静态特征表明,该势能函数准确再现了NaB2和Na2B分子基态平衡结构.     

AlB2和Al2B的结构与解析势能函数

运用单双取代耦合簇(CCSD)方法,选择基组6-311+g(2df)对基态B2、Al2分子和基组6-311g(3df)对基态AlB分子的微观结构进行优化计算,采用最小二乘法拟合得到B2、Al2和AlB分子的势能函数,并得到了与实验值符合很好的光谱常数.采用同种方法,选择6-31g基组,对基态AlB2和Al2B分子的结构进行优化计算.运用原子分子反应静力学原理得到离解极限.在此基础上,采用多体项展式法,得到AlB2和Al2B分子基态解析势能函数,该势能函数准确再现了AlB2和Al2B分子基态平衡结构特征.     

LiB2和Li2B分子的结构与势能函数

运用单双取代耦合簇(CCSD)方法,选择基组6-311+g(2df)对基态B2、Li2和LiB分子的微观结构进行优化计算,采用最小二乘法拟合得到B2、Li2和LiB分子的势能函数,并得到了与实验值符合很好的光谱常数.采用同种方法,选择6-311g基组对LiB2、6-31g基组对Li2B分子的基态结构进行优化计算.运用原子分子反应静力学原理得到离解极限.在此基础上,采用多体项展式法,得到LiB2和Li2B分子基态解析势能函数,该势能函数准确再现了LiB2和Li2B分子基态平衡结构特征.     

MgH分子X2Σ+,A2Π和B2Σ+电子态的势能函数

利用QCISD(T),SAC-CI方法和cc-pVQZ,aug-cc-pVTZ,6-311 G及6-311 G(3df,2pd)基组,对MgH分子的基态X2Σ ,第一简并激发态A2Π和第二激发态B2Σ 的结构进行优化计算.通过对4个基组计算结果进行比较,得出6-311 G(3df,2pd)基组为最优基组.使用6-311 G(3df,2pd)基组和QCISD(T)方法对基态X2Σ ,SAC-CI方法对激发态A2Π和B2Σ 进行单点能扫描计算,然后采用Murrell-Sorbie函数及修正的Murrell-Sorbie C6函数进行拟合,得到了相应电子态的势能函数参数和对应的光谱常数.计算结果表明,用修正的Murrell-Sorbie C6函数计算得到的MgH分子基态和第一简并激发态的光谱常数ωe,ωexe,Be,αe与实验数据吻合很好.表明修正后的Murrell-Sorbie C6函数能更为准确地描述MgH分子的基态和第一激发态的势能函数.     

LiB2和Li2B分子的结构与势能函数

运用单双取代耦合簇(CCSD)方法,选择基组6-311+g(2df)对基态B2、Li2和LiB分子的微观结构进行优化计算,采用最小二乘法拟合得到B2、Li2和LiB分子的势能函数,并得到了与实验值符合很好的光谱常数.采用同种方法,选择6-311g基组对LiB2、6-31g基组对Li2B分子的基态结构进行优化计算.运用原子分子反应静力学原理得到离解极限.在此基础上,采用多体项展式法,得到LiB2和Li2B分子基态解析势能函数,该势能函数准确再现了LiB2和Li2B分子基态平衡结构特征.     

NaH和AlH分子基态(X^1Σ^+)的结构和解析势能函数北大核心CSCD

根据群论及原子分子反应静力学的有关原理,推导出NaH和AlH分子基态(X^1Σ^+)的合理离解极限.使用密度泛函方法中的B3LYP、B3PW91和MPW1PW91方法,在6-311++G,6-311++G(3df,3pd),cc-pVQZ和aug-cc-pVQZ基组下对NaH和AlH分子的基态进行结构优化计算,使用优选的B3PW91/6-311++G(3df,3pd)对基态单点能扫描计算,然后用最小二乘法拟合Murrell-Sorbie函数,得到对应的势能函数参数及光谱常数.结果表明,采用Murrell-Sorbie函数计算所得的光谱常数与实验结果符合的很好,能精确地描述NaH和AlH分子基态的势能函数.     

NaH和AlH分子基态(X~1Σ~+)的结构和解析势能函数

根据群论及原子分子反应静力学的有关原理,推导出NaH和AlH分子基态(X~1Σ~+)的合理离解极限.使用密度泛函方法中的B3LYP、B3PW91和MPW1PW91方法,在6-311++G,6-311++G(3df,3pd),cc-pVQZ和aug-cc-pVQZ基组下对NaH和AlH分子的基态进行结构优化计算,使用优选的B3PW91/6-311++G(3df,3pd)对基态单点能扫描计算,然后用最小二乘法拟合Murrell-Sorbie函数,得到对应的势能函数参数及光谱常数.结果表明,采用Murrell-Sorbie函数计算所得的光谱常数与实验结果符合的很好,能精确地描述NaH和AlH分子基态的势能函数.     

7Li2分子23Σ+g激发态的解析势能函数、谐振频率及振动能级

使用Gaussian03程序包中的"对称性匹配簇/对称性匹配簇-组态相互作用"方法,利用多个基组对7Li2分子23Σ+g态的平衡几何进行了优化计算.同时,在优化得到的平衡位置附近、于同一条件下通过精细的单点能扫描,获得了相应基组下的平衡核间距.发现两者的结果不一致,对不一致的原因进行了解释.分析表明,由单点能扫描得到的平衡核间距应更为合理.同时也得出了6-311++G(3df,3pd),6-311++G(2df,2pd) 及6-311++G(2df,pd)基组均为较优基组的结论.于2.5a0-37a0的范围内利用6-311++G(3df,3pd)基组进行单点能扫描并使用最小二乘法拟合出了该态的解析势能函数.利用解析势能函数的物理意义并结合Rydberg-Klein-Rees方法,计算出了其相应的谐振频率,进而计算了其他光谱常数.为便于比较和分析,对基态也进行了相应的计算.利用得到的解析势能函数,对23Σ+g态的振动能级及振动经典转折点也进行了计算.     

PS(X~2Π_r)基态势能函数与光谱常数研究

根据群论及原子分子反应静力学的有关原理,推导了PS基态分子电子态及其合理的离解极限.采用Gaussian 03软件中的密度泛函理论B3LYP和B3P86结合6-311++G(3df,3pd)、6-311++G、6-311G(3df,3pd)、cc-p VTZ和D95基组,对PS分子基态平衡结构和谐振频率进行了计算.通过比较计算结果,发现B3P86方法结合cc-p VTZ基组计算所得结果与实验值最接近.在该水平下对PS分子的基态进行了单点势能扫描计算,利用正规方程组拟合三参数的Murrell-Sorbie函数和修正的Murrell-Sorbie+C6函数,得到了基态PS分子完整的势能函数与相应的光谱常数ωe、ωexe、Be和αe的值.计算结果表明,利用三参数的Murrell-Sorbie函数计算所得的光谱常数与实验数据吻合得更好.     

用ab initio方法计算NaLi分子基态(X1∑+)的势能函数及光谱常数

运用原子分子群表示方法,首先确定NaLi分子的电子基态(X1∑ ).然后选用6-311 G(3df,2pd)基组优化计算得到NaLi分子基态(X1∑ )的平衡结构和离解能,采用电子相关QCISD(T)方法结合6-311 G(3df,2pd)基组对NaLi分子基态进行单点能扫描计算.最后用单点扫描计算值结合优化计算所得参数去拟合Murrell-Sorbie函数,得到了NaLi分子基态的势能函数.用该势能函数计算的光谱常数与实验结果符合得很好,表明拟合确定的势能函数能精确地描述基态NaLi分子的结构和性质.     

Structural,magnetic and neutron diffraction studies on TbFe2-TbAl2, TbCo2-TbAl2 and HoCo2-HoAl2

Both pseudobinary systems exhibit large homogeneous regions of cubic and hexagonal Laves phases. Ordering tendencies on crystallographic sites between Al and the transition metals are observed in the hexagonal type.Electron transfer to the transition metals quenches their moments so that they become nonmagnetic at high Al concentrations. The peculiarities in the mechanism of magnetization which appear in rare earth dialuminides when Al is replaced by a transition metal have been studied in detail at cryogenic temperatures.The first replacement of Al results in a decrease in saturation moment. Neutron diffraction verifies the low ordered rare earth sublattice moments and reveals the ‘lost part’ as a disordered component. Considerable magnetic hardness develops in certain regions of concentration often connected with spontaneous increases in magnetization with field. All available evidence suggests the presence of unusual domain wall effects to be responsible for this effect. High remanences develop in both the hexagonal and in the cubic structures in the intermediate region. The development of disordered magnetic components is connected either with the disorder on crystallographic sites or changes in the free electron concentration.     

Magnetostriction of SmMn2Ge2 and GdMn2Ge2 intermetallic compounds

Longitudinal and transverse magnetostrictions of polycrystalline samples of intermetallic compounds RMn₂Ge₂ (R=Sm or Gd) are measured in pulsed magnetic fields up to 250 kOe. It is found that linear magnetostrictive strains of about 10^?3 arise in a temperature range in which the magnetic field causes a change in the magnetic state of a manganese magnetic subsystem. The results obtained are described within the model of a two-sublattice ferrimagnet with a negative exchange interaction in the manganese subsystem in terms of a strong dependence of this interaction on interatomic distances.     

Polar optic phonons in Hg2Cl2 and Hg2Br2

Far infrared (30–430 cm^?1) reflectivity measurements of Hg₂Cl₂ and Hg₂Br₂ single crystals have been performed in polarized light. The spectra, which are in agreement with group-theoretical predictions, were analyzed by the oscillator fitting procedure and Kramers-Kronig method. The results are compared with the existing data from other measurements and the large anisotropy of polar modes is briefly discussed. The polarization vectors of all long-wavelength symmetry modes were determined group-theoretically.     

μ+SR study of LaNi2As2, URh2Si2 and CeRh2Si2

Muon spin relaxation experiments have been carried out in the paramagnetic and magnetically ordered states of URh₂Si₂ and CeRh₂Si₂. As the magnetic structure of these compounds is well known, these measurements can help to characterise their magnetic properties probed by μSR and to understand the μSR results of the heavy fermion compounds of the same crystallographic family. Our measurements show that the muons occupy two different crystallographic sites. The spectra of URh₂Si₂ and CeRh₂Si₂ in the magnetically ordered states are very different, probably reflecting their different magnetic structures. The spectra obtained on CeRh₂Si₂ are similar to the published spectra of the heavy fermion compound CeCu_2.1 Si₂. Muon spin rotation measurements on LaNi₂As₂ indicate that the muon is diffusing at 150 K.     

X-ray photoemission spectra measurements of CeNi2Sb2 and CeCu2Sb2

X-ray photoemission spectra, resistivity and susceptibility of CeNi₂Sb₂ and CeCu₂Sb₂ were measured and are discussed. The results indicate that these alloys are Kondo systems. For comparison of the valence band properties, the spectra of the isostructural alloys of RT₂X₂-type with R = La, Gd, T = Cu, Ni and X = Sn, Sb were investigated, too.     

13C-selective IRMPD of CBr2F2/Cl2 and CCl2F2/Br2 systems

The CO₂ TEA laser irradiation of CBr₂F₂ in the presence of Cl₂ yielded ¹³C-enriched CBrClF₂ and ¹³C-enriched CCl₂F₂ under selected experimental conditions. As the photolysis proceeded, the ¹³C concentration of CBrClF₂ decreased gradually and that of CCl₂F₂ increased up to 90% or higher. These results can be explained by the mechanism involving the secondary ¹³C-selective IRMPD of the primary product CBrClF₂. On the other hand, the carbon-containing product for a CCl₂F₂/Br₂ system was only CBrClF₂; the further IRMPD of which probably regenerated CBrClF₂ in the presence of Br₂. The decomposition probabilities of ¹²C- and ¹³C-containing molecules in both systems were measured as functions of laser line, laser fluence, and reactant pressures.     

Magnetic ordering in HoRu2Si2, HoRh2Si2, TbRh2Si2 and TbIr2Si2 by neutron diffraction

Neutron diffraction study of polycrystalline HoRu₂Si₂, HoRh₂Si₂, TbRh₂Si₂, and TbIr₂Si₂ was performed in the temperature range between 4.2 and 300 K. For HoRu₂Si₂ the magnetic spin alignment of a linear transverse wave mode below the Néel temperature 19 K is observed. This static moment wave is propagating along the b-axis with k=(0, 0.2, 0) and is polarized in the c-axis. The root-mean-square and maximum saturation moments per Ho atom are 9.26 and 13.09μ_B, respectively. HoRh₂Si₂, TbRh₂Si₂ an TbIr₂Si₂ are simple collinear antiferromagnets of +-+- type with Néel temperatures of (27±1), (98±2) and (72±3) K, respectively. For TbRh₂Si₂ and TbIr₂Si₂ magnetic moments are localized on RE ions only and are aligned along the tetragonal axis, while for HoRh₂Si₂ they form an angle ø = (28±3)°.