Comparison for σ-hole and π-hole tetrel-bonded complexes involving cyanoacetaldehyde

Ab initio calculations have been performed for the complexes of cyanoacetaldehyde (CA) with TH₃F (T = C, Si, Ge and Sn) and F₂TO (T = C and Si). The σ-hole and π-hole tetrel-bonded complexes are formed for TH₃F and F₂TO, respectively. In general, three minima complexes (N, O–A and O–B) are obtained for each tetrel donor. Most complexes are stabilised by a primary tetrel bond and a secondary hydrogen bonding. TH₃F–N/F₂CO–N has greater stability than TH₃F–O/F₂CO–O, but a reverse result is found in the complexes of F₂SiO although they have comparative interaction energies. Charge transfer from the lone pair on the N/O atom of CA into the T–F σ^* antibonding orbital leads to the stabilisation of the TH₃F complexes. Accordingly, the T–F bond is extended and its stretch vibration displays a redshift. A breakdown of the individual forces involved attributes the stability of the complex mainly to electrostatic energy, with relatively large dispersion term in the CH₃F complexes and relatively large polarisation energy in the F₂SiO complexes.     

Competition between σ-hole pnicogen bond and π-hole tetrel bond in complexes of CF2=CFZH2 (Z = P,As, and Sb)

ABSTRACT

A computational study of the complexes formed by F₂C=CFZH₂ (Z?=?P, As, and Sb) and F₂C=CFPF₂ with two Lewis bases (NH₃ and NMe₃) has been carried out. In general, two minima complexes are found, one with a σ-hole pnicogen bond and the other one with a π-hole tetrel bond in most complexes but two σ-hole pnicogen bonded complexes are obtained for F₂C=CFZH₂ and NH₃. They have similar stability though F₂C=CFSbH₂ engages in a much stronger σ-hole pnicogen bond with NMe₃. The –PF₂ substitution makes the π-hole on the terminal carbon form a tetrel bond with NH₃. A heavier –ZH₂ group engages in a stronger σ-hole pnicogen bond but results in a weaker π-hole tetrel bond. Other than electrostatic interaction, the stability of both complexes is attributed to the charge transfer from the N lone pair into the C–Z/H–Z anti-bonding orbital in the pnicogen bond and the C=C anti-bonding orbital in the tetrel bond.

The σ-hole pnicogen bonded and π-hole tetrel bonded complexes between F₂C=CFZH₂ (Z = P, As, and Sb) and two Lewis bases (NH₃ and NMe₃) have been compared. The results indicate that both interactions can compete, dependent on the nature of the N base.     

On the interplay between particle-hole and Δ-hole phonons

We show that the nuclear polarizability plays a very important role in establishing the magnitude of the Δ-hole polarization effect on the axial-vector coupling constant.     

Level Crossing of N~* (1535)-hole and η Modes and Partial Restoration of Chiral Symmetry in η-mesic Nuclei

We investigate the properties of the η-nucleus interaction by postulating the N~* (1535) dominance for ηN system.Since the mass gap of N~* and N is very close to the η meson mass,there is the possibility of the level crossing between the N~*-h and η modes in finite density.We postulate the N~* (1535) resonance for the ηN system and consider quite distinct N~* properties in finite density which are predicted by two independent chiral models.We find that we can obtain clearer information on the in-medium N~* properties and also on the η-nucleus interaction through the formation of the η-mesic nuclei by (π,N) reactions under the appropriate experimental conditions,which can be performed at existing and/or forthcoming facilities like J-PARC.     

Isoscalar magnetic moments and the role of the δ-hole excitation

Expectation values of the total spinS of nucleons in nuclei are very quenched. This quenching is shown to be hardly explained by the mixture of-hole states. The quenching thus provides the best evidence for the role of non-central parts of the nucleon-nucleon interaction, especially the tensor interaction.     

Competition between hydrogen bond and σ-hole interaction in SCS-HArF and SeCSe-HArF complexes

A computational study of the complexes formed between HArF and XCX (X?=?O, S, and Se) has been performed at the MP2/aug-cc-pVTZ level. Two types of complexes were found. One is formed through a hydrogen bond with XCX as the electron donor and the other is formed through the σ-hole interaction with XCX as the electron acceptor. The OCO-FArH complex is more stable than the OCO-HArF complex, whereas the XCX-HArF (X?=?S and Se) complex is more stable than the XCX-FArH complex. The distant H-Ar bond is shortened and exhibits a blue shift, but the associated one displays a red shift in SCS-HArF and SeCSe-HArF complexes. When compared with XCX-HF complex, the structure of the complex suffers a great effect from the inserted noble gas atom. The natural bond orbital (NBO) and atoms in molecules (AIM) have been performed for a better understanding of the interactions.     

Cooperative interaction between π-hole and single-electron σ-hole interactions in O2S···NCX···CH3 and O2Se···NCX···CH3 complexes (X = F,Cl, Br and I)

Ab initio calculations are performed to analyse the cooperative effects between π-hole and single-electron σ-hole interactions in O₂S···NCX···CH₃ and O₂Se···NCX···CH₃ complexes, where X = F, Cl, Br and I. These effects are investigated in terms of geometric and energetic features of the complexes, which are computed by UMP2/aug-cc-pVTZ(-PP) method. Our results indicate that the shortening of the each π-hole bond distance in the complexes is dependent on the strength of the σ-hole interaction. The maximum and minimum energetic cooperativity values correspond to the most and least stable complexes studied in the present work. The cooperativity between both types of interaction is chiefly caused by the electrostatic effects. The topological analysis, based on the quantum theory of atoms in molecules, is used to characterise the interactions and analyse their enhancement with varying electron density at bond critical points.     

Co~(2 )-Ti~(4 )和Cu~(2 )-Nb~(5 )离子取代BaFe_(12)O_(19)单晶体中Fe~(3 )离子的研究

本文对用Co~(2 )-Ti~(4 )和Cu~(2 )-Nb~(5 )离子取代BaFe_(12)O_(19)单晶体中Fe~(3 )离子进行了研究,以Bi_2O_3作为助熔剂生长出了BaFe_(12-2x)Co_x~(2 )Ti_x~(4 )O_(19)(x=0;0.04;0.09;0.13;0.27和0.68)以及BaFe_(12-x)[Nb_(1/3)~(5 )Cu_(2/3)~(2 )]_xO_(19)(x=0;0.28;0.44和0.60)这两系列的单晶体,测定了100—300K温度范围内样品的磁化强度σ与单轴各向异性常数K_1,我们发现,对CO~(2 )-Ti~(4 )取代的样品,当x≤0.09时,其σ与K_1随x的增加而缓慢增加;当x>0.09时,其σ与K_1随x的增加而迅速降低,至x=1.1时,K_1变为零,对Nb~(5 )-Cu~(2 )取代的样品,其σ值在整个成份范围内基本保持不变,且有缓慢增加趋势;而K_1值则随x增加而单调下降,提出了取代离子在M型六角铁氧体中可能的分布模型来解释我们的结果。     

金属玻璃(Fe_(1-x)Co_x)_(78)Si_(10)B_(12)的感生各向异性

本文研究了金属玻璃(Fe_(1-x)CO_x)_(78)Si_(10)B_(12)的磁化感生各向异性、应变感生各向异性随成分和温度的变化。磁化感生各向异性常数K_(um)为正值,x=0.7时为最大;不可逆的应变感生各向异性常数K_(usi)为正值,x=0.5时为最大;可逆的应变感生各向异性常数K_(usr)除了x>0.975区均为负值,在x=0.7时为最大;感生各向异性常数在温度变化时与M_s~α成正比,α在3.4和7.5之间随成分和退火工艺而变化。用短程有序模型解释了部分实验结果。     

Pb_(0.50)Sr_(0.75)Y_(0.70)Ca_(0.25)Cu_(1.70)O_y单晶的磁阻研究

对低掺杂区非超导的Pb_(6.56)Sr_(?)Y_(?)Ca_(?)Cu_(?)O_y单晶样品进行了电阻和磁阻的测量,发现在低温下电阻温度关系遵从变程跳跃传导的R=R_(?)exp[(T_(?)/T)~(?)]的变化规律,这说明该样品处于强局域化区域.在低温下的磁阻为负并有明显的各向异性,这表明这类体系的磁阻主要来自于轨道效应的贡献,并且可能受到自旋-轨道散射的影响.     

非晶态Fe_(100-x)B_x、(Fe_(1-x)Co_x)_(84)B_(16)和(Fe_(1-x)Ni_x)_(84)B_(16)合金的电阻率与温度的关系

用四端引线法测量了Fe_(100-x)B_x(12≤x≤24)、(Fe_(1-x)Co_x)_(84)B_(16)(0.02≤x≤0.08)和(Fe_(1-x)Ni_x)_(84)B_(16)(0.02≤x≤0.08)非晶态合金的电阻率与温度的关系。实验结果得到,这三个非晶态合金系列在低温区都呈现出电阻率极小,极小值的温度T_(min)都在20K以下。电阻率极小的出现认为是类Kondo效应的贡献。在T>T_(min)温区,电阻率与温度的关系用推广的Ziman理论作了解释。     

金属玻璃(Cu_(1-x)Ni_x)_(33)Zr_(67)的超导电性

本文研究了金属玻璃(Cu_(1-x)Ni_x)_(33)Zr_(67)的超导电性.测量了超导转变温度T_c、上临界磁场H_c_2和其它重要物理量.结果分析表明:这些金属玻璃属于弱耦合超导体.随着Ni含量增多,T_c提高.由(dH_c_2/dT)_(T_c)的测量得到费米面上电子态密度N(0).Varma-Dynes参数δ粗略地是常数.较高的N(0)相应于较高的T_c.N(0)是支配超导行为的基本参量.     

非晶态Fe_(13)Ni_(67.2)P_(4.5)B_(15.3)合金的临界现象

本文报道非晶态Fe_(13)Ni_(67.2)P_(4.5)B_(15.3)合金的磁化强度与温度和磁场关系的测量结果。在居里温度附近样品的磁特性符合二级相变规律,得到临界指数β=0.39±0.02,γ=1.56±0.06,δ=5.20±0.1,样品的居里温度T_c=(180.4±0.2)K。在实验误差范围内,临界指数β,γ,δ满足γ=β(δ-1)关系,在168—192K温度范围,实验数据满足二级相变的磁状态方程。当T>270K时,样品顺磁磁化率服从居里-外斯定律,由居里-外斯常数c计算出有效顺磁磁矩 P_(eff)=3.19μ_B。     

关于Pb~(208)附近原子核的能谱(Ⅰ) Pb~(205)和Pb~(204)

利用独立粒子模型的观点、用分波的方法,将两体相互作用当作微扰来处理。并且认为在计算能谱中,三体以上核子之间的相互关连不重要,对Pb~(205)及Pb~(204)两个原子核的能级进行了计算。所得结果与实验符合得很好。     

BaMgAl_(10)O_(17)∶Eu~(2 )的MgF_2表面包覆(英文)

采用溶胶-凝胶法对蓝色荧光粉BaMgAl10O17∶Eu2 (BAM)进行表面包膜处理,获得了表面均匀包覆MgF2膜层的BAM荧光粉。并用SEM、XRD和IR手段对其表面形貌、晶格结构性能进行了表征;用EDS对BAM粉体的表面元素进行了定性分析;用荧光光谱测试对荧光粉的发光性能进行了研究。结果表明,在BAM粉体表面均匀包覆MgF2层后,BAM的晶格结构,发光性能没有改变,初始亮度较未包覆的荧光粉有所降低,经过相同条件的热处理后,包覆MgF2荧光粉的亮度热衰减程度明显低于未包覆的荧光粉,且色坐标偏移现象不明显。     

非晶态Fe_(13.3)Ni_(69.6)B_(16.2)Si_(0.9)的结构驰豫

本文讨论了非晶合金Fe_(13.3)Ni_(69.6)B_(16.2)Si_(0.9)的结构弛豫动力学及可逆弛豫过程,研究了各种热处理引起居里温度T_C的变化。发现经长时间退火后T_C趋于平衡值且动力学可通过弛豫时间连续谱加以描述。可逆弛豫过程可用CSRO来说明,并且某一物理量的可逆变化并不意味着整个结构的变化是可逆的。     

U(N) SP(N) O(3)的分支律

利用群的直乘分解公式,考虑U(N)群的[2a1b]表示按群链U(N)SP(N)O(3)的约化规则,给出了相应的比较简单的分支律递推公式.该公式在用计算机计算分支律时,不受秩和表示维数的限制.为求解这类问题的分支律提供了一种比较简单的算法.在简化同位旋1/2的单j费米子体系的母分系数计算中具有十分重要的意义.用同样的方法也可以求出群链U(N)O(N)O(3)的分支律.     

~(59)Co(n,p)~(59)Fe,~(59)Co(n,α)~(56)Mn,~(59)Co(n,2n)~(58)Co反应截面的测量

本实验用活化法测量了中子能量在12.8MeV到17.8MeV的~(59)Co(n,p)~(59)Fe,~(59)Co(n,α)~(56)Mn,~(59)Co(n,2n)~(58)Co三个反应道的反应截面值,实验的测量误差在3.3％—6.9％范围内. 本文还计算了反应截面测量误差的协方差矩阵,并将实验测量值与理论计算值进行了比较.另外,还对上述三个反应道的截面进行编评,给出了推荐的激发曲线.     

~(186)W(d,p)~(187)W,~(186)W(d,2n)~(186)Re,~(nat)Fe(p,x)~(56)Co和~(nat)Ti(a,x)~(51)Cr反应激发函数评价

考虑特征γ射线分支比、衰变常数和标准截面等修正,对带电粒子引起的核反应~(186)W(d,p)~(187)W,~(186)W(d,2n)~(186)Re,~(nat)Fe(p,x)~(56)Co和~(nat)Ti(a,x)~(51)Cr的激发函数进行了研究。全面收集了这些反应激发函数的实验测量数据,对这些实验数据进行了分析处理,应用数学方法对分析处理后的实验数据进行了拟合。经过评价,给出了50 Me V以下~(186)W(d,p)~(187)W,~(186)W(d,2n)~(186)Re,~(nat)Fe(p,x)~(56)Co和~(nat)Ti(a,x)~(51)Cr反应激发函数的推荐值。     

High-Resolution Spectroscopy of Jet-Cooled (32)SO(2) and (34)SO(2): The ã(3)B(1)-;X(1)A(1), 2(1)(0) and 1(1)(0) Bands

Laser-induced excitation spectra of the two bands ?(3)B(1)-;X(1)A(1), 2(1)(0) and 1(1)(0) of (32)SO(2) and (34)SO(2) have been recorded in a supersonic jet at a resolution of 0.015 cm(-1). The rotational and electron-spin fine structure has been analyzed for both isotopic species. Analysis of the rotational and electron-spin fine structure yields precise values of the rotational constants A, B, and C and the spin constants alpha and beta for both (32)SO(2) and (34)SO(2) in the states ?(3)B(1) (010) and (100). No interaction between these two vibrational states with any nearby triplet state is observed for rotational levels with J 相似文献