The Green function with an insertion of the gauge-invariant twist-four operator O(x) = − 1 4 (F μν u ) 2 is calculated to one-loop order in the light-cone gauge. We show that the renormalization requires gauge-nonin...
The Green function with an insertion of the gauge-invariant twist-four operator O(x) = − 1 4 (F μν u ) 2 is calculated to one-loop order in the light-cone gauge. We show that the renormalization requires gauge-noninvariant counterterms satisfying the Slavnov-Taylor identity.
In recent work on the structure of water I have exploited both time-of-flight neutron diffraction (TOF) and conventional reactor neutron diffraction to extract the hydrogen-hydrogen correlation function in liquid wate...
In recent work on the structure of water I have exploited both time-of-flight neutron diffraction (TOF) and conventional reactor neutron diffraction to extract the hydrogen-hydrogen correlation function in liquid water using the technique of hydrogen/deuterium substitution. Because the dynamic effects on the TOF data have a very different dependence on momentum transfer ( Q ) from those for the reactor data, the two sets of data offer a unique opportunity to establish an estimate of the magnitude of the dynamic correction. Apart from a discrepancy at small Q which is not fully understood at present, the different diffraction techniques show good agreement over most of the Q range. The comparison is used to discuss the applicability of the H/D subtraction (which involves no arbitrary fitting parameters) to molecular liquids in general: the main features in the structure factors can be determined readily. On the other hand, it is likely that finer details such as quantum effects will be obscured by experimental imitations.
We study the stability criterion for the critical point of a transition of the second kind in the T-H Q plane of an antiferromagnetic superconductor AFS (T is temperature and H Q is the staggered molecular field). The...
详细信息
We study the stability criterion for the critical point of a transition of the second kind in the T-H Q plane of an antiferromagnetic superconductor AFS (T is temperature and H Q is the staggered molecular field). The AFS is described by using the mean-field model given by Nass, Levin and Grest and we assume a one dimensional electron band. Some properties of the system near the critical point are also investigated.
Gamma rays from a radioisotope source, 241 Am, are scattered from samples of light water (H 2 O) and heavy water (D 2 O) at temperature 297 K and density 0.0334 molecules/Å 3 to determine what differences occur i...
Gamma rays from a radioisotope source, 241 Am, are scattered from samples of light water (H 2 O) and heavy water (D 2 O) at temperature 297 K and density 0.0334 molecules/Å 3 to determine what differences occur in their structure factors. The apparatus, method of data collection and data analysis are described in detail. The results are compared to the predictions of a computer simulation, in which ground state librational motion of rigid molecules causes significant quantum effects in the site-site correlation functions of the two liquids. Differences between our data and the simulation suggest that coupling occurs between intramolecular and intermolecular modes, and influences the structure of water. It is noted that the structural changes due to quantum effects are similar to those that occur in water upon formation of a 0.55 M solution of LiOH.
Recent Raman and infrared spectra of a number of tetrahalide crystals are reported. While some examples of isotopic and crystal field splittings of the internal molecular modes are included, the emphasis is on the ext...
Recent Raman and infrared spectra of a number of tetrahalide crystals are reported. While some examples of isotopic and crystal field splittings of the internal molecular modes are included, the emphasis is on the external lattice vibrations which are important for investigations of intermolecular forces and lattice dynamics calculations. Because of the weak signals from these non-polar near-spherical molecules and other experimental difficulties, these modes have not been investigated in detail in earlier work. Examples to be discussed include CCl 4 , CBr 4 and CF 4 , all of which exhibit solid state phase transitions; the tetrachlorides of Ge, Ti, Si and Sn, all of which are thought to have similar crystal structures; and SnBr 4 , the structure of which is accurately known and is used as a basis for lattice dynamics calculations.
The equation of motion of a 17-particle chain with anharmonic nearest neighbour forces have been numerically integrated for 101 different initial conditions. The 101 stored histories constitute a constant energy ensem...
The equation of motion of a 17-particle chain with anharmonic nearest neighbour forces have been numerically integrated for 101 different initial conditions. The 101 stored histories constitute a constant energy ensemble. The time dependence of the coarse grained mode Boltzmann H functions indicates that the ensemble evolves reversibly from an initial non-equilibrium state to a final equilibrium state characterized by a minimum in each mode H function. There is no equipartition of energy among the modes.
Low-frequency Raman and far-infrared spectra of both solid phases of CH 3 CN and CD 3 CN at temperatures between 20 K and the melting point have been recorded. Assignment of the observed peaks as librations about the ...
Low-frequency Raman and far-infrared spectra of both solid phases of CH 3 CN and CD 3 CN at temperatures between 20 K and the melting point have been recorded. Assignment of the observed peaks as librations about the principal molecular axes or as translational modes is facilitated by finding the frequency ratios of corresponding peaks for CH 3 CN and CD 3 CN. The spectra are compared with group theoretical predictions, based on possible space groups for each of the two phases. It is found that a unit cell with point group C 2 h and four molecules on general sites is favoured for phase I. The lattice spectra do not appear to be compatible with the larger unit cell proposed for phase II.
NbTe4 is a quasi-one-dimensional metallic compound. The crystal structure is tetragonal and is modulated by an incommensurate distortion wave at room temperature. We show that on the cooling of the crystal into the te...
NbTe4 is a quasi-one-dimensional metallic compound. The crystal structure is tetragonal and is modulated by an incommensurate distortion wave at room temperature. We show that on the cooling of the crystal into the temperature range 100-50 K, two distinct sets of sharp spots can occur along the streaks that arise in the diffraction patterns. There are indications that the two types can occur in different parts of the same crystal. The interpretation of the observations in terms of discommensuration arrays is discussed.
It is demonstrated that the close matching between the minima in the interionic potentials and the maxima of the partial pair-distribution functions, proposed in the literature as a necessary condition for the stabili...
It is demonstrated that the close matching between the minima in the interionic potentials and the maxima of the partial pair-distribution functions, proposed in the literature as a necessary condition for the stability of metallic glasses, does not exactly apply to the transition-metal glasses. In addition, a realistic interionic potential is suggested for the glass-structure calculation.
It is demonstrated that a recently described ab initio variational thermodynamic calculation for pure liquid metals can be significantly improved by using the hard-sphere Yukawa model instead of the usual hard-sphere ...
It is demonstrated that a recently described ab initio variational thermodynamic calculation for pure liquid metals can be significantly improved by using the hard-sphere Yukawa model instead of the usual hard-sphere model as the reference system.
暂无评论