Heat capacity and phonon dispersion in poly(L-methionine)

Poly(L -methionine) (PMet) is one of the two sulfur containing polyamino acids. Raman, FTIR spectra, and heat capacity measurements of PMet have been well interpreted through the normal mode analysis and the density of states derived therefrom. Earlier interpretation of heat capacity data is limited because it is based on the Tarasov model, wherein the concept of group frequency and skeletal similarity are used. A special feature of some dispersion curves is their tendency to bunch in the neighborhood of the helix angle. This has been attributed to the presence of strong intramolecular interactions. Repulsion between the dispersion curves is also observed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2281–2292, 1997     

Analytical Expressions for Ising Models on High Dimensional Lattices

We use an m-vicinity method to examine Ising models on hypercube lattices of high dimensions d≥3. This method is applicable for both short-range and long-range interactions. We introduce a small parameter, which determines whether the method can be used when calculating the free energy. When we account for interaction with the nearest neighbors only, the value of this parameter depends on the dimension of the lattice d. We obtain an expression for the critical temperature in terms of the interaction constants that is in a good agreement with the results of computer simulations. For d=5,6,7, our theoretical estimates match the numerical results both qualitatively and quantitatively. For d=3,4, our method is sufficiently accurate for the calculation of the critical temperatures; however, it predicts a finite jump of the heat capacity at the critical point. In the case of the three-dimensional lattice (d=3), this contradicts the commonly accepted ideas of the type of the singularity at the critical point. For the four-dimensional lattice (d=4), the character of the singularity is under current discussion. For the dimensions d=1, 2 the m-vicinity method is not applicable.     

Trace Distance of Remote State Preparation Through Noisy Channels

In this paper, we study remote state preparation (RSP) by w state through noisy channels. The trace distance is used to describe how close the original state is to the output state. Studies show the trace distance is a function of decohenrence rates and angles of the state to be prepared. At the same time, we investigate the influence of different types of noises on the trace distance and find the various types of noises have different degrees of influence on the trace distance for a definite qubit. We also study changes of the trace distance against polar and azimuthal angles.     

MLi2H3(M=Na,K)与NH3反应的密度泛函理论研究

采用杂化密度泛函方法,对MLi₂H₃(M=Na, K)团簇与NH₃的反应机理进行计算分析,对反应中各驻点几何构型进行优化,经频率分析和内禀反应坐标计算以确证各驻点的正确性和连接关系.经单点能校正计算,给出反应相关的能量信息.结果表明：引入Na和K原子后,反应物LOMO轨道有大幅度的向Na、K原子处的转移. KLi₂H₃有较小的能隙和电离势及较高的费米能,有较高反应活性. Na、K元素的引入,能破坏反应物的稳定性,降低反应能垒.     

The convolution theorem and the Franck–Condon integral

The convolution theorem is used to evaluate the Franck–Condon integral. It is shown that this integral becomes the matrix element between two “squeezed” states. This enables one to evaluate the integral by using boson operators. In addition, a general method is developed to obtain integrals involving Hermite polynomials with a displaced argument. In particular, the two‐center matrix element _g〈m|f(x_e)|n〉_e, is obtained, where f(x_e)=exp(Dx+Fx_e). ©1999 John Wiley & Sons, Inc. Int J Quant Chem 75: 11–15, 1999     

An Exceedingly Stable Diiron(II,III) Complex Ion [(tz){Fe(CN)5}2]5− with Comproportionation Constants between 108 (in H2O) and 1019 (in CH3CN)

A record equilibrium constant of K _c = 10 ¹⁹ was found for the comproportionation of the diiron(II ,III ) complex 1 in acetonitrile. In water the K_c value is strongly diminished (10^7.9), but still exceeds that of the Creutz–Taube ion. Intervalence charge transfer bands occur at 2520 nm (in CH₃CN) and 2250 nm (in D₂O), and all evidence points to a strongly coupled system with delocalized valences.     

Synthetic Diamond — Basic Research and Applications

Non-equilibrium growth of synthetic diamond layers by chemical vapour deposition (CVD) techniques on heterosubstrates has largely been improved over the past decade. On silicon substrates highly textured and oriented diamond films can be grown with optical transparencies and thermal conductivities suitable for broad-band optical windows and heat spreaders. Boron pulse-doping of homoepitaxial diamond layers leads to high p-conductivity at room temperature allowing the fabrication of Schottky diodes and field effect transistors operating at temperatures up to 1000 K. Other devices such as sensors and detectors are being successfully fabricated. At the same time many basic questions remain to be solved including efficient n-type doping.     

Density Functional Theory Calculations Revealing Metal‐like Band Structures and Work Function Variation for Ultrathin Gallium Arsenide (111) Surface Layers

Density functional theory (DFT) calculations have been performed on tunable numbers of gallium arsenide (100), (110), and (111) planes for their electron density of states (DOS) plots and the corresponding band diagrams. The GaAs (100) and (110) planes show the same semiconducting band structure with tunable plane layers and a band gap of 1.35 eV around the Fermi level. In contrast, metal‐like band structures are obtained with a continuous band structure around the Fermi level for 1, 2, 4, 5, 7, and 8 layers of GaAs (111) planes. For 3, 6, and 9 GaAs (111) planes, the same semiconducting band structure as seen in the (100) and (110) planes returns. The results suggest the GaAs {111} face should be more electrically conductive than its {100} and {110} faces, due to the merged conduction band and valence band. GaAs (100) and (110) planes give a fixed work function, but the (111) planes have variable work function values that are smaller than that obtained for the (100) and (110) planes. Furthermore, bond length, bond geometry, and frontier orbital electron number and energy distribution show notable differences between the metal‐like and semiconducting plane cases, so the emergence of plane‐dependent electronic properties have quantum mechanical origin at the orbital level. GaAs should possess similar facet‐dependent electronic properties to those of Si and Ge.     

Exact Solutions to the Quantum Rabi-Stark Model Within Tunable Coherent States

The quantum Rabi-Stark model, where the linear dipole coupling and the nonlinear Stark-like coupling is present on an equal footing, is studied within the tunable extended coherent states. The eigenvalues and eigenstates are therefore obtained exactly. Surprisingly, the entanglement entropy in the ground-state is found to jump suddenly with the coupling strength. The first-order quantum phase transition can be detected by level crossing of the ground state and the first excited state, which is however lacking in the original linear quantum Rabi model. Performing the first-order approximation in the present theory, we can derive closed-form analytical results for the ground-state. Interestingly, it agrees well with the exact solutions up to the ultra-strong coupling regime in a wide range of model parameters. The spectral collapses when the absolute value of the nonlinear coupling strength approaches to twice the cavity frequency is observed with the help of new solutions in the limits.     

Translational cooling of doped nanocrystals by Raman pulses: Towards macroscopic quantum state

One of the most interesting problems of modern physics is the realization of nanoparticles in macroscopic quantum states, in which they behave as a quantum objects. These states can only be implemented at ultra-low translational temperatures that have not been achieved so far. Here we develop a novel method for optical cooling of CaF₂:Yb³⁺ nanocrystals, which is based on the coherent population transfer induced in the impurity ions by ultraviolet Raman pulses. A doped nanocrystal localized in a radio-frequency trap is cooled due to the photon recoil from the pulses of varied intensity. The proposed method allows to obtain nanocrystals with translational temperatures of the order of 10^?9 K, which indicates that the nanocrystal approaches a macroscopic quantum state.