MRCI+Q study of the low-lying electronic states of CdF including spin-orbit coupling

Cd F molecule, which plays an important role in a great variety of research fields, has long been subject to numerous researchers. Due to the unstable nature and heavy atom Cd containing in the Cd F molecule, electronic states of the molecule have not been well studied. In this paper, high accurate ab initio calculations on the Cd F molecule have been performed at the multi-reference configuration interaction level including Davidson correction（MRCI ＋ Q）. Adiabatic potential energy curves（PECs） of the 14 low-lying Λ–S states correlating with the two lowest dissociation limits Cd（~1S_g） ＋ F（~2P_u） and Cd（~3P_u） ＋ F（~2P_u） have been constructed. For the bound Λ–S and ？ states, the dominant electronic configurations and spectroscopic constants are obtained,and the calculated spectroscopic constants of bound states are consistent with previous experimental results. The dipole moments（DMs） of 2 Σ＋ and 2Π are determined, and the spin–orbit（SO） matrix elements between each pair of X2Σ＋, 22Σ＋, 12Π, and 22Π are obtained. The results indicate that the sudden changes of DMs and SO matrix elements arise from the variation of the electronic configurations around the avoided crossing region. Moreover,the Franck–Condon factors（FCFs）, the transition dipole moments（TDMs）, and radiative lifetimes of low-lying states-the ground state X2Σ＋are determined. Finally, the transitional properties of 22Π–X2Σ＋and 22Σ＋–X2Σ＋are studied. Based on our computed spectroscopic information of Cd F, the feasibility and challenge for laser cooling of Cd F molecule are discussed.

Investigation of the Spin Crossover Complex [Fe(bapbpy)(NCS)_2 ] in Its Low-spin and Highspin State by DFT/TD-DFT/BS-DFT Calculations

The spin crossover（SCO） compound [Fe（bapbpy）（NCS）2],where bapbpy contains two fused N,N-bis（2-pyridyl）amines,has been studied by DFT/TD-DFT/BS-DFT methods.Several density functionals and basis sets were used in the calculation to obtain optimized geometries of the compound in the low-（LS） and high-spin（HS） states.The vibrational modes and IR spectra,spin splitting energies,excited states and UV/Vis absorption spectra were obtained.The structural parameters of the calculated isolated complex are in good agreement with the X-ray data.We investigate three dimers of [Fe（bapbpy）（NCS）2] complex for their magnetic properties.It has been found that the complex（1,3） has ferromagnetic character while the others are antiferromagnetic in nature by using a broken symmetry approach in the DFT framework（BS-DFT） with support from the coupling constant values（J） and spin density plots.

Spin correlations in the S = 1 armchair chain Ni_(2)NbBO_(6) as seen from NMR

We report our nuclear magnetic resonance(NMR) study on the structurally spin chain compound Ni_(2)NbBO_(6) with complex magnetic coupling.The antiferromagnetic transition is monitored by the line splitting resulting from the staggered internal hyperfine field.The magnetic coupling configuration proposed by the first-principle density functional theory(DFT) is supported by NMR spectral analysis.For the spin dynamics,a prominent peak at T~35 K well above the Neel temperature(T_(N)~20 K at μ0 H=10 T) is observed from the spin-lattice relaxation data.As compared with the dc-susceptibility,this behavior indicates an antiferromagnetic coupling with the typical energy scale of ~3 meV.Thus,the Ni_(2)NbBO_(6) compound can be viewed as strongly ferromagnetically coupled armchair spin chains along the crystalline b-axis.These facts place strong constraints on the theoretical model for this compound.

The Quantization of Space

In the present work, it will be shown that the dimensionless number 137 of the fine-structure constant α demands a quantization of space. For this purpose, we refer to a volume constant of electromagnetic processes, which takes effect as a volume quantum. This involves not only a re-evaluation of the Dirac equation but also, and above all, a determination of Einstein’s velocity vector as the fundamental property of these processes. A prerequisite is the linking of the hydrogen spectrum with the hydrogen nucleus.

Study of spin sum rules (and the strong coupling constant at large distances)

We present recent results from Jefferson Lab on sum rules related to the spin structure of the nucleon. We then discuss how the Bjorken sum rule with its connection to the Gerasimov-Drell-Hearn sum, allows us to conveniently define an effective coupling for the strong force at all distances.

Multireference calculations on low-lying states and the X^3 Π_u -~3 Π_g absorption spectra of indium dimers

Multireference configuration interaction calculations are carried out on 11 Λ–S low-lying electronic states of indium dimers. The states are investigated with spin–orbit pseudopotentials via the state-interacting method, and characterized by fitted spectroscopic constants based on computed potential energy curves. The vibrational structures of the double-potential well 0^＋g （I） （ ^3 Σ g^- ） state are also analyzed. The experimentally observed absorption spectrum centred at ～ 13000cm-1 is simulated and assigned to X 3 Πu （v＇=0）–3Πg transition according to the present ab initio calculations on transition energies and dipole moment functions.

Further investigations of the low-lying electronic states of AsO^+ radical

The high level quantum chemistry ab inito multi-reference configuration interaction （MRCI） method with large V5Z basis set is used to calculate the spectroscopic properties of the 15 A-S electronic states （X1∑＋, A I П, 1 △, 1 ∑, 3∑＋, 3П, 3△, 3△ , 5∑＋, 5П, 5△, 1П （II）, ofAsO＋ radical correlated to the dissociation limit As＋（3pg） ＋ O（3pg） and As＋（IDg） ＋ O（1Dg）. In order to obtain better potential curves and more accurate spectroscopic properties, the Davidson modification is taken into account. With the potential energy curves （PECs） determined here, vibrational levels G（v） and inertial rotation constants Bu are computed for all the bound electronic states when the rotational quantum number J equals zero （J = 0）. Except for the states X1∑＋, A1П , it is the first time that the multi-reference configuration calculation has been used on the 13 A-S electronic states of the AsO＋ radical. The potential energy curves of all the A-S electronic states are depicted according to the avoided crossing rule of the same symmetry. Spin-orbit coupling effect （SOC） is introduced into the states X1 ∑＋, A1 П, 3П to consider its effects on the spectroscopic properties. Transition dipole moments （TDMs） from A1П 1, 3 П1 states to the ground state X1∑0＋ are predicted as well.

旋轨耦合作用对BeH分子光谱特性的影响

基于旋轨耦合作用(SOC)下多组态准简并微扰理论(MCQDPT),计算了BeH分子基态X^(2)∑^(+)和第一激发态A^(2)∏_(r)的分裂电子态的势能函数参数、力常数和光谱常数,并描绘了以上电子态的势能函数曲线。结果表明:旋轨耦合作用下X^(2)∑^(+)未发生分裂,A^(2)∏_(r)分裂为电子态^(2)∏_(1/2)和^(2)∏_(3/2);2个分裂电子态间的垂直跃迁能较大(76.7349 cm^(-1)),表明旋轨耦合作用对第一激发态影响显著;且计算出的2个分裂电子态的光谱常数精确度较高。

金刚石NV色心系综内14N核自旋测量与调控

金刚石内氮空位(NV)色心中的氮核自旋是一个原子级别磁结构,无法如同NV电子自旋一样在任意磁场下受光泵浦极化。随机指向的氮核自旋缩短了NV色心电子自旋的相干时间,限制了NV色心电子自旋的传感测量能力。通过激光、微波和射频脉冲共同作用完成NV色心中氮核自旋的磁共振测量和调控,表明其可以被调控和初始化。研究结果表明,NV色心中的14N核自旋在2.79、4.95和7.11 MHz处具有共振信号。测量得到的核自旋系综Rabi信号在11个π脉冲的脉冲宽度射频作用后仍然具有明显相干性,而电子自旋系综在7个π脉冲的脉冲宽度微波作用后已经完全退相干,表明其具有远优于NV电子自旋的相干性质。引入单个π脉冲脉冲宽度的射频信号后,14N核自旋在一个态上的布居数降低了50%。这项工作可为在基于NV色心的传感测量应用中引入核自旋调控提升传感能力提供技术支撑。

Application of Product Operator Formalism to the Strongly Coupled Spin (I=1/2) Systems

Product operator formalism has been developed to evaluate, in closed analytical form, the time evolution for strongly coupled spin (I=1/2) systems. This formalismis based on two facts: (ⅰ) the Hamiltonian for a strongly coupled spin system is a zero-quantum operator and when an arbitrary zero-quantum operator acts on a p-quantum operator, what is yielded is still a p-quantum operator and can be expressed in terms of a linear combination of a complete p-quantum operator base set of the spin system; (ⅱ) the zeroquantum and unitary transformation leads the Hamiltonian to be only a linear combination of zero-quantum longitudinal magnetization and spin order operators. Thus the time evolution for the spin systems can be evaluated in closed analytical form. The formalism retains completely the original character of the product operator formalism and enlarges its applicability. It can deal with both strongly and weakly coupled spin (I=1/2) systems in united and closed analytical forms.

A local spin evaluation into the active site models of [2Fe2S] ferrodoxin [Fe_2S_2(SR)_4]^(2-) (R=-H, -CH_3)

To test the feasibility of local spin theory of Davidson and Clark for ferrodoxin clusters, the models [Fe2S2(SR)4]2- (R=-H, -CH3) are chosen for evaluation. This purpose is realized by calculating the local spin expectation values <S_A·S_B>, <S_A^2 >, and mA and discussing the connection between these expected values and the Heisenberg spin model (HSM) and the Noodleman broken-symmetry approach. In practical calculation, the spin-unrestricted Hartree-Fock (UHF) and spin-polarized density functional theory (DFT) are used and the calculational qualities of these two methods are also discussed. In addition, the theoretical magnetic coupling constants JAB of these models are calculated by various computational schemes for comparison with both theoretical and experimental results previously reported.

C-F键核自旋偶合常数的理论研究

利用密度泛函中B3LYP方法 ,选择 6 31G 基组 ,研究了四组分别为 1 0、2 0、30、40个分子的C F键的核自旋偶合常数 ,由此拟合出 4个计算核自旋偶合常数的公式 ,并用 4种化合物分别进行检验 ,理论计算值较好地与文献值相符合 .

直接键连原子间的NMR偶合常数的自然杂化轨道研究V.^(13)C-^(13)C和^(13)C-^(31)P核自旋偶合常数~1J_(CC)和~1J_(CP)

在前文工作的基础上，结合ＭＮＤＯ／ＥＨＭＯ分子轨道方法和自然杂化轨道方法，具体计算了ＣＣ键和ＣＰ键的核自旋偶合常数．计算结果表明，１ＪＣＣ和１ＪＣＰ主要由成键原子的轨道杂化作用和键极性这两种结构因素所决定．为从简单价键理论角度解释和计算１ＪＣＣ和１ＪＣＰ值提供了简便直观的方法．

直接键链^(13)C-~1H的核自旋偶合常数的理论研究

用一种计算直接键链原子核自旋偶合常数1 JA B的统一的半经验关系式 ,研究了各种代表性的环状分子及非环状分子的1 JC H的核自旋偶合常数 ,计算值与实验值吻合的较好 ,说明该统一的半经验关系式既可适用于非环状分子又可适用于环状分子化合物体系的直接键链原子的核自旋偶合常数1 JC

直接键连原子间的NMR偶合常数的自然杂化轨道研究

首次报道了直接计算偶合常数￣１Ｊ＿（ＣＮ）和￣１Ｊ＿（ＣＦ）的线性关系式，结果表明，￣１Ｊ（ＣＮ）和￣１Ｊ＿（ＣＦ）主要由成键原子的轨道杂化作用和键极性这两种结构因素所决定，且偶合相互作用中的Ｆｅｒｍｉ接触项仍是最主要的．为从简单价键理论角度解释并计算Ｊ＿（ＣＮ）和Ｊ＿（ＣＦ）的值提供了简便直观的方法．

直接键连原子间的NMR偶合常数的自然杂化轨道研究Ⅲ、α─C─H键核自旋偶合常数￣（1）J＿（cH）

报道了一种计算直接键连原子间的核自旋─自旋偶合常数的通用关系式，结合ＣＮＤＯ／２分子轨道方法和自然杂化轨道方法，具体计算了一些极性α─Ｃ─Ｈ键的核自旋偶合常数。结果表明，本文方法适合于多种类型的直接键连原子间的偶合常数的计算，且与已有实验值吻合一致．

C-P(V)键核自旋偶合常数的理论研究

利用自然杂化轨道 ,以从头算级别的理论计算方法 ,选择较小基组STO 3G ,研究了C -P(V)键的核自旋偶合常数 ,并用三种化合物进行验证 ,理论计算值较好地与文献值相符合。

卤代甲烷系列谱学性质与结构关系的研究

本文借助最大重迭杂化轨道理论研究了卤代甲烷系列分子的NMR自旋-自旋偶合常数和核四极偶合常数与结构的关系。较明确地反映了化学键性质和取代基对分子谱学性质的影响。

SiH^(+)(X^(1)∑^(+))的势能曲线、光谱常数、振转能级和自旋-轨道耦合理论研究

基于Molpro 2012程序包,应用包含Davidson修正的多参考组态相互作用方法,使用AVXZ和AVXdZ(X=T,Q,5,6)基组进行单点能从头算,然后采用Aguado-P aniagua函数进行拟合,得到了 SiH^(+)(X^(1)∑^(+))离子在不同基组、不同方法和是否考虑自旋-轨道耦合(SOC)情况下的解析势能函数(APEFs).以APEFs为基础,计算了SiH^(+)(X^(1)∑^(+))离子的解离能De,平衡键长Re,振动频率ωe,光谱常数Be,αe和ωeχe,同时讨论了 SOC对该体系的影响.本文的计算结果与其他理论计算符合得较好,与实验数值也基本吻合.基于SOC-AV6dZ方法下的APEF,通过求解径向薛定谔方程,给出了SiH^(+)(X^(1)∑^(+))离子的前23个振动能级(j=0),并详细列出了每1个振动能级及其相应的经典拐点,每个振动态的转动常数和6个离心畸变常数,且提供了振动能级图.该工作对于实验和后续的理论工作有参考和指导作用.

采用BP神经网络研究C-F键核自旋偶合常数

通常理论研究核自旋偶合常数的方法是基于线性模型进行拟合和预测,该方法在拟合和预测中仍有较大误差.本文在前面工作的基础上,提出了基于非线性模型对C-F键核自旋偶合常数进行研究的观点,采用BP神经网络方法对C-F键核自旋偶合常数的函数关系式进行拟合,并用拟合结果对4种化合物的偶合常数进行预测.结果表明,采用非线性的BP神经网络方法其训练效果与预测效果均优于线性模型方法;其预测误差对文中的4种化合物不超过0.40%.