On isotropic states in α-LiNH4SO4 crystals

The spectral and baric dependences of the birefringence of α-LiNH₄SO₄ crystals are studied. It is found that the birefringence is rather sensitive to uniaxial compressions. A baric shift of the isotropic point to longer or shorter wavelengths depending on the uniaxial compression direction is observed and a generalized temperature-spectral-baric diagram of the isotropic state is plotted. A possibility of the appearance of a pseudoisotropic state under the action of uniaxial pressure σ _z or simultaneous pressures σ _x = σ _z is shown.     

Reductive cleavage of O-, S-, and N-organonitroso compounds by nickel(I) beta-diketiminates

An electron-rich nickel(I) beta-diketiminate cleaves the E-NO bond of O-, S-, and N-organonitroso species to give the nickel nitrosyl [Me 3NN]NiNO along with dimeric nickel(II) alkoxide or thiolate complexes {[Me 3NN]Ni} 2(mu-E) 2 or the mononuclear nickel(II) amide [Me 3NN]NiNPh 2. This diamagnetic three-coordinate amide exhibits temperature-dependent NMR spectra due to a low-lying triplet state.     

Neutral high-potential nickel triad bisdithiolenes: structure and solid-state NMR properties of Pt[S2C2(CF3)2]2

X-ray crystallography and solid-state NMR techniques were used to determine the structure and 195Pt NMR chemical shift (CS) tensor of Pt[S2C2(CF3)2]2. This is the first reported crystal structure of a highly oxidizing (CN- or CF3-substituted) neutral bis(dithiolene) complex of a Ni triad metal in its pure form. The 195Pt NMR CS tensor is highly anisotropic and asymmetric; the latter property is attributed to the noninnocent nature of the ligand. The tensor components and orientation are determined with density functional theory calculations.     

A statistical mechanics view of quantum chromodynamics: Lattice gauge theory

Recent developments in lattice gauge theory are discussed from a statistical mechanics viewpoint. The basic physics problems of quantum chromodynamics (QCD) are reviewed for an audience of critical phenomena theorists. The idea of local gauge symmetry and color, the connection between statistical mechanics and field theory, asymptotic freedom and the continuum limit of lattice gauge theories, and the order parameters (confinement and chiral symmetry) of QCD are reviewed. Then recent developments in the field are discussed. These include the proof of confinement in the lattice theory, numerical evidence for confinement in the continuum limit of lattice gauge theory, and perturbative improvement programs for lattice actions. Next, we turn to the new challenges facing the subject. These include the need for a better understanding of the lattice Dirac equation and recent progress in the development of numerical methods for fermions (the pseudofermion stochastic algorithm and the microcanonical, molecular dynamics equation of motion approach). Finally, some of the applications of lattice gauge theory to QCD spectrum calculations and the thermodynamics of. QCD will be discussed and a few remarks concerning future directions of the field will be made.Supported in part by the NSF under grant No. PHY82-01948