Modern Physics Letters B

We consider the dynamics of a dimer of the organic salt N-methyl-M-ethylmorpholinium-tetracyanoquinodimethane [MEM(TCNQ)₂] in the presence of an external precessing magnetic field. We derive the influence of Berry's phases on the magnetization and electric dipole moment per site of the organic salt in the adiabatic limit.

In the case of a spherical blast wave described by the Sedov–Taylor model in an ideal gas, we apply the Vashy–Buckingham theorem (Pi theorem) to take into account the pressure of the medium at rest, and consequently the internal energy of the gas at rest. We obtain a single formula which contains the full time behavior of the explosion from the very beginning (Sedov–Taylor solution) up to the sound wave, therefore describing analytically the transition phase from t = 0 until t → ∞.

In this paper, the crystal structures of a series of diborides are analyzed based on the hard ball model. We show that the packing efficiency has a close relation with the lattice parameter ratio c/a and the closest packing is achieved at c/a = 1.074. For the compounds with c/a < 1.074, the packing is loose along the basal plane and the B–B bond is under compression while with c/a > 1.074 the packing is loose along the c-direction and the B–B bond is stretched. The structures will be unstable as the c/a value deviates from 1.074. MgB₂ has the largest value of c/a among the examined diborides, except for lanthanide diborides and YB₂.

A series of ferroelectric ceramics with the compositional formula PbZr_0.52Ti_0.48O₃ + x wt% of Nb₂O₅ were prepared by the solid state reaction method. Samples were characterized by studying their X-ray diffraction and dielectric measurements. The longitudinal and shear wave velocities and corresponding elastic moduli were determined at room temperature by using the pulse transmission technique. The values of Young's modulus (E), and the rigidity (n) and bulk (k) moduli were corrected to theoretical density and were found to increase with increasing dopant concentration. The variation of elastic moduli and other elastic parameters such as Debye temperature (θ_D) with composition are explained qualitatively.

Surface and volume crystallization of amorphous, melt-quenched (Ni₅₀Zr₅₀)_99.9P_0.1 alloy has been investigated by measurements of the temperature dependencies of the intensity of photostimulated exoelectron emission (EEE) and by differential scanning calorimetry (DSC). A comparison of these dependencies enables one to assess the tendency of the investigated materials to premature surface crystallization. For the (Ni₅₀Zr₅₀)_99.9P_0.1 alloy the surface crystallization occurs at temperatures distinctly lower than that for the crystallization in bulk. The activation energy for the surface crystallization, determined by the Ozawa method, i.e. from the shift of EEE peak corresponding to the surface crystallization on changing the heating rate, is also much lower than that for the volume crystallization.