Theoretical study on the spectroscopic properties and electronic structures of heteroleptic phosphorescent Ir(III) complexes

The geometries, spectroscopic and electronic structures properties of a series of heteroleptic phosphorescent Ir(III) complexes including N981, N982, N983, N984 have been characterized by density functional theory calculations. The excited‐state properties of the Ir(III) complexes have been characterized by CIS method. The ground‐ and excited‐state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. By using the time‐dependent density functional theory method, the absorption and phosphorescence spectra were calculated based on the optimized ground‐ and excited‐state geometries, respectively. The results show that the absorption and emission data agree well with the corresponding experimental results. The calculated results also revealed that the nature of the substituent at the 4‐position of the pyridyl moiety can influence the distributions of HOMO and LUMO and their energies. In addition, the charge transport quality has been estimated approximately by the calculated reorganization energy (λ). Our result also indicates that the positions of the substitute groups not only change the transition characters but also affect the charge transfer rate and balance, and complex N982 is a very good charge transfer material for green OLEDs. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Theoretical studies on structures and electronic spectra of linear carbon chains C2nH+ (n = 1−5)

The density functional theory (DFT) and the complete active space self‐consistent‐field (CASSCF) method have been used for full geometry optimization of carbon chains C_2nH⁺ (n = 1–5) in their ground states and selected excited states, respectively. Calculations show that C_2nH⁺ (n = 1–5) have stable linear structures with the ground state of X³Π for C₂H⁺ or X³Σ^? for other species. The excited‐state properties of C_2nH⁺ have been investigated by the multiconfigurational second‐order perturbation theory (CASPT2), and predicted vertical excitation energies show good agreement with the available experimental values. On the basis of our calculations, the unsolved observed bands in previous experiments have been interpreted. CASSCF/CASPT2 calculations also have been used to explore the vertical emission energy of selected low‐lying states in C_2nH⁺ (n = 1–5). Present results indicate that the predicted vertical excitation and emission energies of C_2nH⁺ have similar size dependences, and they gradually decrease as the chain size increases. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

ONIOM Study of Isomerization Reactions of Aromatic Hydrocarbons in Acidic Mordenite Zeolite

Two different mechanisms : Shift 1,2‐isomerization and isomerization via the disproportionation reaction are investigated for aromatic hydrocarbons over acidic mordenite zeolite by using our own n‐layered integrated molecular orbital and molecular mechanics (ONIOM) scheme. The picture shows a schematic energy profile for the isomerization of toluene catalyzed by acidic mordenite.

     

Multilayered model in optics and quantum mechanics

Three types of dispersion equations are analyzed that describe the eigenvalues of the effective refractive index of a multilayer plane optical waveguide and the energy eigenvalues of a quantum particle placed in a piecewise constant potential field. The first equation (D1) is derived by setting to zero the determinant of the system of linear equations produced by matching the solutions in the layers. The second equation (D2) is obtained using the well-known method of characteristic matrices. The third equation has been obtained in the general case by the author and is known as a multilayer equation. Simple relations between the three equations are established. It is shown that the set of roots of D2 exactly coincides with the set of eigenvalues of the multilayer problem, while the roots of D1 and the multilayer equation contain those equal to the refractive index in the optical case (or to the potential in the quantum case) in internal layers of the system, which may be superfluous. Examples are presented.     

跳过程的$\mu$-不变测度————-含吸收态情形

本文对给了全稳定含吸收态的$q$-对的$\mu$-不变测度,何时存在$q$-过程$P(t)$,使得$\pi$是$P(t)$的$\mu$-不变测度的问题进行了讨论研究,并给出了两个充要条件.     

Thermodynamic properties of Ag2O--B2O3 glasses by a modified scale-transformed energy space sampling Monte Carlo method

The density of states of Ag(2)O--B(2)O(3) glasses has been calculated by using a modified scale-transformed energy space sampling algorithm. This algorithm combines the scale-transformed energy space sampling algorithm and the Wang-Landau method. It is shown how the two algorithms can be combined to improve the efficiency of calculation. The thermodynamic properties, in particular the specific heat C(V), of the above-mentioned glass system is studied. At temperatures above 80 K, the value of specific heat C(v) is close to 22 J/mol/K. At low temperatures, the deviations of C(v) from a T(3) behavior are discernible, that is, C(v)/T(3) exhibits a hump at T = 7 K, which is in good agreement with the reported experimental behavior.     

An Energy Interconversion Principle Applied in Reaction dynamics for the determination of equilibrium standard states

Chemical and other reaction theories involving thermodynamical equilibrium states utilize statistical mechanical equilibrium density distributions. Here, a definition of heat-work transformation termed thermo-mechanical coherence is first made, and it is conjectured that most molecular bonds have the above heat-work transformation property, which models a chemical bond as a “centrifugal heat engine”, where the internal energy state need not correspond to any of the standard equilibrium densities. Expressions are derived for the standard Gibbs free energy, enthalpy, and entropy where the bond coordinates need not conform to a non-degenerate Boltzmann state, since bond breakdown and formation are processes that have direction, whereas equilibrium distributions are derived when the Hamiltonian is of fixed form, which is not the case for chemical reactions using localized Hamiltonians. The empirically determined Gibbs free energy from a known molecular dynamics simulation of a dimer reaction , accords rather well with the theoretical estimate. A relation connecting the rate of reaction with the equilibrium constant and other kinetic parameters is derived and could place the commonly observed linear relationship between the logarithms of the rate constant and equilibrium constant on a firmer theoretical footing. These relationships could include analogues of the Hammett correlations used extensively in physical organic chemistry, as well as others which are temperature dependent. One prediction of the principles developed here is that the equilibrium standard reaction free energy is more dependent on the height of the intermolecular potential than its depth, so that the sign of the ΔG ^θ can change for varying barrier height with fixed well depth, which may appear counter-intuitive. All the above developments can be tested directly in simulations and therefore provides a fertile ground for further research with significant implications on how standard states are determined in relation to the direction of chemical reaction.This work treats the molecular bond using standard thermodynamics as if it were a system, and it is anticipated that with the advent of single-molecule science and experiment, that might be one direction in which molecular statistical thermodynamics would develop.     

CdTe(110)表面原子与电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理计算了CdTe(110)表面的原子和电子性质.结果表明,CdTe(110)理想表面在禁带中出现两个明显的表面态,弛豫后表层Cd原子和Te原子p态电子发生转移,Cd原子趋向于sp2平面杂化构型,Te原子趋向p3杂化的锥形构型.经过表面弛豫大大降低了表面能,增大了表面功函数,表面占据态和表面空态分别被推进价带顶之下和导带底之上,导致弛豫表面没有明显的表面态.     

Local density of states around two nonmagnetic impurities in cuprate superconductors

The local density of states (LDOS) around two nonmagnetic impurities which are located at different sites is studied within the two-dimensional t-J-U model. The order parameters are determined in a self-consistent way with the Gutzwiller projected mean-field approximation and the Bogoliubov-de Gennes theory. When the two impurities are located one or two sites away, we find the superconductivity coherence peaks are more strongly suppressed and the zero-energy peak (ZEP) has split into two peaks. Whereas when the two impurities are located next to each other, the ZEP vanished, and LDOS does not change a lot compared with the case away from the impurities.     

Teleportation of three-dimensional single particle state in noninertial frames

Considering the spin degree of freedom of the Dirac field, we study the entanglement behavior of a different class of communication channel and teleportation of three-dimensional single particle state in noninertial frames. Numerical analysis shows that the communication channel in our scheme can offer enough distillable entanglement for the teleportation protocol. Moreover, the teleportation protocol could work well if Rob＇s acceleration is not very big, but the fidelity of the teleportation is still reduced due to the Unruh effect.