Vibrational spectra of nucleic acid bases and their Watson–Crick pair complexes

The vibrational spectra of the nucleic acid bases adenine, thymine, guanine, and cytosine are calculated in the frame of density functional theory (DFT). In particular we use the Kohn–Sham scheme with gradient corrections for exchange and correlation to determine normal modes, frequencies, and intensities. The DFT results are found to be in good agreement with the experiment. Our computations provide assignments for IR, Raman, and neutron inelastic scattering spectroscopies; yield characteristic vibrational fingerprints of each compound for its identification in larger systems; and show general vibrational trends of nucleic acids. The Kohn–Sham scheme is further applied to obtain the spectra of the Watson–Crick pairs adenine-thymine and guanine-cytosine. A large number of monomeric vibrations are recognized in dimers; characteristic vibrations of pairs, which are mainly attributed to hydrogen bridges, are quantified according to changes in normal modes and frequency shifts. Binding and zero-point vibrational energies are analyzed to establish the stability of the complexes and discuss the quality of the energetic calculations. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 511–530, 1999     

Quark-Quark Interaction with Confinement Terms in a QCD-Based Model Field Theory

Based on the determined bilocal field in the global color symmetry model, the effective quark-quark interaction is deduced explicitly in this letter. The result shows that, except for the normal one-π and one-σ exchange terms, the confinement terms with screening factors can automatically be obtained.     

Quantum computation of the properties of helium using two-body and three-body intermolecular potentials: a molecular dynamics study

We have performed the molecular dynamics simulation to obtain energy, pressure, and self-diffusion coefficient of helium at different temperatures and densities using Lennard–Jones (LJ), Hartree–Fock dispersion-Individual damping (HFD-ID) potential, and the HFD-like potential which has been obtained with an inversion of viscosity data at zero pressure supplemented by quantum corrections following the Feynman–Hibbs approach. The contribution of three-body interactions using an accurate simple relationship reported by Wang and Sadus between two-body and three-body interactions has been also involved for non-effective potentials (HFD-ID and HFD-like) in simulation. Our results show a good agreement with corresponding experimental data. A comparison of our simulated results with other molecular simulations using different potentials is also included.     

Standard and SUSY Higgs production at the LHC

Recent theoretical developments concerning Higgs production at the large hadron collider are reviewed, both in the standard model and in the MSSM. Emphasis is put on the inclusive and exclusive cross-sections for gluon fusion, as well as on the associated production with bottom quarks.     

无序瞬子媒质中的三胶子凝聚

在有限温度量子色动力学（ＱＣＤ）瞬子真空模型中，考虑瞬子间的相互作用，应用费曼变分原理和平均场近似，研究了三胶子凝聚的温度依赖性．结果表明：三胶子凝聚随温度升高而衰减，并在Ｔ≈３．０Ａｍｓ时几乎为零，三胶子凝聚的干涉部分与非干涉部分相比可以忽略，低温近似仅在Ｔ＜６０ＭｅＶ温度区域成立     

Trap-recharging waves versus damped,forced charge-density oscillations in hexagonal silicon carbide

The structural parameters and hydrostatic pressure coefficients of CdS_xTe_1-x in the two phases, namely zinc-blende and NaCl as well as the transition pressures from zinc-blende to NaCl structures at various S concentrations are presented. The calculations are performed using the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the local density approximation (LDA), and two developed refinements, namely the generalized gradient approximation (GGA) of Perdew et al. for the structural properties and Engel-Vosko for the band structure calculations. Detailed comparisons are made with published experimental and theoretical data and show generally good agreement. The present results regarding the studied quantities for compositions x in the 0–1 range (0 < x < 1) and for the NaCl phase are predictions and may serve as a reference for experimental work.     

Interpretation of the NuTeV experiment

The NuTeV neutrino measurement of the Weinberg angle differs by 3 standard deviations from measurements at the Z pole. We review the status of various possibilities to explain this result, including contributions from physics outside the standard model; effects of radiative corrections; nuclear corrections to parton distributions; isospin-violating effects; and effects due to strange quarks.     

Ab initio study of structural,electronic and dynamical properties of MgAuSn

The structural and electronic properties of MgAuSn in the cubic AlLiSi structure have been studied, using density functional theory within the local density approximation. The calculated lattice constant for MgAuSn is found to be in good agreement with its experimental value. Our calculated electronic structure is also compared in detail with a recent tight-binding. A linear-response approach to density-functional theory is used to calculate the phonon spectrum and density of states for MgAuSn.     

First principles study of the electronic structures of erbium silicides with non-frozen 4f treatment

The electronic structures (especially 4f states) of hexagonal and tetragonal erbium silicides are investigated within density functional theory. Contrary to previous theoretical studies on these compounds, Er 4f electrons are treated as valence state electrons, explicitly taking into account the on-site Coulomb interactions. Total energy calculations show that the relaxed hexagonal ErSi_1.7 is more stable than the tetragonal structure, consistently with related experimental observations. The calculated total density of states of the hexagonal ErSi_1.7 agrees well with the experimental valence-band spectrum in a wide energy range from 0 to 12 eV below the Fermi level. In addition, our study indicates that the occupied 4f states in erbium silicides can also locate in the energy range of 0–4.0 eV below the Fermi energy, much different from the prediction of the previously adopted Er ion model.     

Optical spectrum and local lattice structure for ruby

We perform ab initio calculations using a pseudo-potential plane-wave method based on density functional theory, within the local density approximation and generalized gradient approximation, in order to determine and predict the pressure dependence of structural and elastic properties of spinel compounds: MgAl₂O₄, MgGa₂O₄ and MgIn₂O₄. The results are in agreement with the available experimental data and other theoretical calculations.