Interaction and arrangement of nitrogen and carbon atoms in fcc γ-iron

A Mössbauer effect measurement has been done for Fe?N, Fe?Al?C and Fe?Ni?C austenite in order to study the interaction between the interstitial atoms and their distribution among the octahedral sites of the fcc lattice, together with the influence of Al and Ni atoms. The spectra for Fe?N and Fe?Al?C austenite are decomposed into three components; one singlet γ₀, and two sets of doublet γ₁ and γ₂, with different quadrupole splittings, while no γ₂ component is found in the spectrum for Fe?Ni?C. By analyzing the component ratio in each spectrum, it is concluded that, in Fe?N and Fe?Al?C, the interaction between 2nd nearest neighboring nitrogen or carbon atoms is attractive, and is repulsive between 1st nearest for Fe?N, and that the interaction between 2nd nearest atoms is repulsive for Fe?Ni?C. By measuring the spectra of Fe?Ni?C in magnetic field, the sign of EFG for most of the γ₁ component is determined to be negative.     

Abelian surfaces in projective toric 4-folds

We show fundamental properties on embedding of abelian surfaces into projective toric 4-folds, and study the case of the toric Del Pezzo 4-fold from the viewpoint of the moduli space of abelian surfaces with polarization of type (1, 5). Received: 31 January 2005; revised: 15 April 2005     

Discrete Dynamical Systems with W(A (1) m−1 × A (1) n−1) Symmetry

We give a birational realization of affine Weyl group of type A ⁽¹⁾ _m–1 × A ⁽¹⁾ _n–1. We apply this representation to construct some discrete integrable systems and discrete Painlevé equations. Our construction has a combinatorial counterpart through the ultra-discretization procedure.     

Pressure-induced phase transition in Sb2Te3

An anomalous change in electrical resistance with pressure was observed in crystalline Sb₂Te₃ around 80 kbar at room temperature. This anomaly was found to be closely related with a pressure-induced structural phase transition which is discovered by the present x-ray diffraction experiment.     

Phase transitions in N—n-propylpyridinium-TCNQ2 and N—n-butylpyridinium-TCNQn at high pressures

The electrical resistivity of N-n-propylpyridinium-TCNQ₂ (NPPy-TCNQ₂) and N-n-butylpyridinium-TCNQ_n (NBPy-TCNQ_n) has been measured as a function of temperature and pressure. Phase transitions in these salts have been studied at high pressures. The transition temperature (T_c) in NPPy-TCNQ₂ at atmospheric pressure increased with increasing pressure at the rate of dT_c/dP = + 12.0 degkbar^?1. The value of volume change calculated from the Clapeylon-Clausius relation was + 4.4 cm³ mol^?1. The electrical resistivity along the a- and c-axis increased with increasing pressure below 7 kbar. This anomalous electrical behaviour is closely related to the crystal structure of NPPy-TCNQ₂. The resistivity dropped sharply at about 11 kbar. This abrupt change may be due to a new pressure induced phase transition.The T_c of the NBPy-TCNQ_n increased remarkably with increasing pressure up to 0.7 kbar, above which the phase transition disappeared. The phase transitions of N-n-alkyl-substituted pyridinium TCNQ salts depend strongly on the nature of cations.