Methyl orbital signatures in 2-amino-1-propanol

Electron density distributions of 2-aminoethanol (2AE) and 2-amino-1-propanol (2AP) are calculated in both the coordinate and the momentum spaces using the B3LYP/TZVP method. Using the dual space analysis, molecular orbital signatures of the methyl substituent in 2AP are identified with respect to 2AE. Relaxations of the geometry and the valence orbital in 2AP are found to be due to the insertion of the methyl group. Five orbitals, not four orbitals, are identified as the methyl signatures. They are orbital 5a in the core shell, orbitals 9a and 10a in the inner valence shell, and orbitals 15a and 16a in the outer valence. In the inner valence shell, the attachment of methyl to 2AE causes a splitting of its orbital 8a into orbitals 9a and 10a of 2AP, whereas in the outer valence shell, the methyl group results in the insertion of an additional orbital pair of 15a and 16a. The frontier molecular orbitals 21a, 20a, and 19a are found to have no significant role in the methylation of 2AE.     

Synthesis and Vibrational Spectroscopic Investigation of Methyl L-Prolinate Hydrochloride: A Computational Insight

In our present work, methyl L-prolinate hydrochloride has been synthesized from L-proline amino acid and characterized by Fourier transform infrared and Fourier transform Raman spectra via experimental and computational methods. Ab initio Hartree-Fock and density functional theory (B3LYP) calculations have been made for the structure, and atomic charge distributions were also predicted for the title compound by using the 6-311++G(d,p) basis set. Predicted vibrational frequencies have been assigned and compared with experimental Fourier transform infrared and Fourier transform Raman spectra. The thermodynamic properties such as heat capacity, enthalpy, entropy, and Gibbs energy have been calculated at different temperatures. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energy show the charge transfer behavior within the molecule.     

First-principles study of orbital ordering in cubic fluoride KCrF_3

Comprehensive first-principles calculations are performed to provide insight into the intriguing physical properties of the ternary cubic fluoride KCrF3. The electronic structures exhibit a prominent dependence on the effective local Coulomb interaction parameter Ueff. The ground state of the cubic phase is a ferromagnetic （FM） half-metal with Ueff equal to 0, 2, and 4 eV, whereas the insulating A-type antiferromagnetic （A-AFM） state with concomitant homogeneous orbital ordering is more robust than the FM state for Ueff exceeding 4 eV. We propose that the origin of the orbital ordering is purely electronic when the cooperative Jahn-Teller distortions are absent in cubic KCrF3.     

Measuring multi-configurational character by orbital entanglement

ABSTRACT

One of the most critical tasks at the very beginning of a quantum chemical investigation is the choice of either a multi- or single-configurational method. Naturally, many proposals exist to define a suitable diagnostic of the multi-configurational character for various types of wave functions in order to assist this crucial decision. Here, we present a new orbital-entanglement-based multi-configurational diagnostic termed Z_s(1). The correspondence of orbital entanglement and static (or non-dynamic) electron correlation permits the definition of such a diagnostic. We chose our diagnostic to meet important requirements such as well-defined limits for pure single-configurational and multi-configurational wave functions. The Z_s(1) diagnostic can be evaluated from a partially converged, but qualitatively correct, and therefore inexpensive density matrix renormalisation group wave function as in our recently presented automated active orbital selection protocol. Its robustness and the fact that it can be evaluated at low cost make this diagnostic a practical tool for routine applications.     

Assessment of delocalized and localized molecular orbitals through electron momentum spectroscopy

Recently, there was a hot controversy about the concept of localized orbitals, which was triggered by Grushow＇s work titled ＂Is it time to retire the hybrid atomic orbital？＂ [J. Chem. Educ. 88, 860 （2011）]. To clarify the issue, we assess the delocalized and localized molecular orbitals from an experimental view using electron momentum spectroscopy. The delocalized and localized molecular orbitals based on various theoretical models for CH4, NH3, and H20 are compared with the experimental momentum distributions. Our results show that the delocalized molecular orbitals rather than the localized ones can give a direct interpretation of the experimental （e, 2e） results.     

Flat band localization due to self-localized orbital

We discover a new wave localization mechanism in a periodic wave system, which can produce a novel type of flat band and is distinct from the known localization mechanisms, i.e., Anderson localization and flat band lattices. The first example we give is a designed electron waveguide (EWG) on 2DEG with special periodic confinement potential. Numerical calculations show that, with proper confinement geometry, electrons can be completely localized in an open waveguide. We interpret this flat band localization (FBL) phenomenon by introducing the concept of self-localized orbitals. Essentially, each unit cell of the waveguide is equivalent to an artificial atom, where the self-localized orbital is a special eigenstate with unique spatial distribution. These self-localized orbitals form the flat bands in the waveguide. Such self-localized orbital induced FBL is a general phenomenon of wave motion, which can arise in any wave systems with carefully engineered boundary conditions. We then design a metallic waveguide (MWG) array to illustrate that similar FBL can be readily realized and observed with electromagnetic waves.     

苯乙烯与苯酚反应的前线轨道理论分析

采用密度泛函理论的M062X方法和6-311G(d,p)基组,对苯乙烯与苯酚的反应进行了分子轨道理论计算.通过讨论反应过程中各分子的最高占据轨道(HOMO)和最低空轨道(LUMO),预测了化学反应的方向和相应的反应产物.经过前线轨道理论分析,得出苯乙烯与苯酚反应的关键步骤是形成苯乙烯基碳正离子,反应中H+起到催化作用;反应产物主要有4-(1-苯基乙基)苯酚、2-(1-苯基乙基)苯酚、2,4-双-(1-苯基乙基)苯酚、2,4,6-三-(1-苯基乙基)苯酚(SP-3)、1,3-二苯基丁烯和4-(1,2-二苯丙基)苯酚.     

苯乙烯与苯酚反应的前线轨道理论分析

采用密度泛函理论的M062X方法和6-311G(d,p)基组,对苯乙烯与苯酚的反应进行了分子轨道理论计算。通过讨论反应过程中各分子的最高占据轨道(HOMO)和最低空轨道(LUMO),预测了化学反应的方向和相应的反应产物。经过前线轨道理论分析,得出苯乙烯与苯酚反应的关键步骤是形成苯乙烯基碳正离子,反应中H+起到催化作用;反应产物主要有4-(1-苯基乙基)苯酚、2-(1-苯基乙基)苯酚、2,4-双-(1-苯基乙基)苯酚分子、2,4,6-三-(1-苯基乙基)苯酚(SP-3)、1,3-二苯基丁烯和4-(1,2-二苯丙基)苯酚。     

C60外价简并轨道电子相关性质的DFT研究

用密度泛函理论(DFT)方法研究C60分子的外价能量简并轨道的动量分布、空间电子密度分布等基本性质.取DFT理论中的B3LYP方法在6-311 G的基组上分析了C60分子最外层5个简并轨道(Hu)的动量分布及轨道电子的密度分布,并进行相关分析.     

异丁烷分子内价轨道的电子动量谱学研究

在高分辨率电子动量谱仪上首次获得了异丁烷分子 (Isobutane)的结合能谱和动量谱的实验结果 ,并用HF和DFT方法做了理论计算。实验结果与理论计算符合较好。     

Valence orbital method of calculating harmonic emission from diatomic molecule

We present a valence orbital method of calculating high-order harmonic generation from a diatomic molecule with arbitrary orientation by using a space rotation operator. We evaluate the effects of each valence orbital on harmonic emissions from N₂ and O₂ molecules in detail separately. The calculation results confirm the different properties of harmonic yields from N₂ and O₂ molecules which are well consistent with available experimental data. We observe that due to the orientation dependence of \sigma and \pi orbitals, the bonding orbital (\sigma _{2pz} )^2 of N₂ determines the maximum of harmonic emission when the molecular axis of N₂ is aligned parallel to the laser vector, and the magnitude of the high harmonic signal gradually weakens with the orientation angle of molecular axis increasing. But for O₂ molecule the antibonding orbitals (\pi _{2py}^\ast )^1 and (\pi _{2pz}^\ast )^1 contribute to the maximum of harmonic yield when O₂ is aligned at 45^{\circ} and bonding orbitals (\pi _{2py} )^2 and (\pi _{2pz} )^2 slightly influence the orientation angle of maximum of harmonic radiation not exactly at 45^{\circ}.     

环戊烯分子内价轨道1a′的电子动量谱学研究

报道了环戊烯（C₅H₈）分子1a′轨道的电子动量谱，并且给出了价 轨道的电离能谱信息 .实验在非共面对称几何条件下用能量多道型电子动量谱仪完成，入射电子的能量为1200 eV 加结合能.通过Hartree-Fock 和密度泛函方法计算得到了C₅H₈分子 1a′轨道的动量谱. 对1a′轨道的电子动量谱的实验值和理论计算进行了比较，得到了该轨道的极强度（pole s trength）的信息.     

利用光束的轨道角动量实现高密度数据存储的机理研究

光束的轨道角动量本征态可以构建高维Hilbert空间，将之应用于数据存储中，可以实现比传统方法更高的数据存储密度.提出了一种用光束轨道角动量实现高密度数据存储的方法，对存储区域进行相位编码，通过探测透射光束轨道角动量谱(螺旋谱)的特征来区分由相位编码形成的不同数据态.四台阶结构相位编码可以实现57个不同的数据态，有望将数据密度提高为传统方法的近6倍. 关键词： 光束轨道角动量 光学存储 高密度存储     

阿比特龙的红外光谱与前线轨道

采用密度泛函理论的B3LYP混合泛函和6-311G(d,p)基组,通过几何结构优化得到了阿比特龙分子的稳定构型.计算了阿比特龙分子的红外吸收光谱,并与文献数据进行比较,将2971.01、1588.31、1536.13、1450.40、1112.13和1074.44 cm~(-1)等处吸收峰指认为特征吸收峰.在优化计算的基础上,结合Multiwfn软件分析了阿比特龙分子的前线轨道成分,得出阿比特龙分子的亲核能力明显强于其亲电能力,C55、O54原子在95αHOMO中占据的权重分别为61.79%和17.05%,C=O-H部位是其亲核反应的活性中心.研究结果对阿比特龙分子的检测、活性应用等方面具有一定的理论指导意义.     

一维自旋-轨道模型中的畴状轨道液体态

研究了一个一维可解自旋-轨道模型.在大自旋极限下，自旋自由度可以近似用经典自旋来描 述.在没有外磁场情形，系统的基态是伊辛自旋反铁磁背景下的轨道液体态.其低能元激发是 类似于spinon的轨道量子.而在有外磁场情形，系统会出现磁通点阵相.同时，磁通将系统分 割成不连通的轨道液体. 关键词： 自旋轨道系统 畴状轨道液体     

丁酮分子内价轨道1a″的电子动量谱学研究

用高分辨率电子动量谱仪进行丁酮分子的结合能谱和内价轨道1a″电子动量谱的实验工作，以及用Hartree-Fock和密度泛函理论方法对1a″轨道电子动量谱的理论研究. 得到了各价轨道的电离能值以及理论计算的总能、偶极矩和1a″轨道的二维密度图. 并比较了内价轨道1a″的电子动量谱的实验和理论计算结果，实验结果与理论计算符合较好.     

环戊烯分子内价轨道1a′的电子动量谱学研究

报道了环戊烯（C₅H₈）分子1a′轨道的电子动量谱，并且给出了价 轨道的电离能谱信息 .实验在非共面对称几何条件下用能量多道型电子动量谱仪完成，入射电子的能量为1200 eV 加结合能.通过Hartree-Fock 和密度泛函方法计算得到了C₅H₈分子 1a′轨道的动量谱. 对1a′轨道的电子动量谱的实验值和理论计算进行了比较，得到了该轨道的极强度（pole s trength）的信息.     

Orbital responses to methyl sites in CnH2n＋2 （n= 1-6）

Orbital responses to methyl sites in C_nH_2n+2 （n=1-6） are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method.Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space.The highest occupied molecular orbital （HOMO） investigations indicate the pelectron profiles in methane,ethane,propane,and n-butane.By increasing the number of carbon-carbon bonds in lower momentum regions,the s,p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space （P<0.50 a.u.）.Meanwhile,the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds,meaning that more electrons have contributed to orbital construction.The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space.An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space.However,such shifts are greatly reduced in the outer valence space.Meanwhile,the opposite energy shift trend is found in the intermediate valence space.