Aleksandr Ivanovich Potapov September 27, 1949–February 9, 2010

Chronicle

Aleksandr Ivanovich Potapov September 27, 1949–February 9, 2010     

Rotational Spectra of CH3CCH–NH3, NCCCH–NH3, and NCCCH–OH2

Microwave spectra of NCCCH–NH₃, CH₃CCH–NH₃, and NCCCH–OH₂have been recorded using a pulsed-nozzle Fourier-transform microwave spectrometer. The complexes NCCCH–NH₃and CH₃CCH–NH₃are found to have symmetric-top structures with the acetylenic proton hydrogen bonded to the nitrogen of the NH₃. The data for CH₃CCH–NH₃are further consistent with free or nearly free internal rotation of the methyl top against the ammonia top. For NCCCH–OH₂, the acetylenic proton is hydrogen bonded to the oxygen of the water. The complex has a dynamicalC_2vstructure, as evidenced by the presence of two nuclear-spin modifications of the complex. The hydrogen bond lengths and hydrogen-bond stretching force constants are 2.212 Å and 10.8 N/m, 2.322 Å and 6.0 N/m, and 2.125 Å and 9.6 N/m for NCCCH–NH₃, CH₃CCH–NH₃, and NCCCH–OH₂, respectively. For the cyanoacetylene complexes, these bond lengths and force constants lie between the values for the related hydrogen cyanide and acetylene complexes of NH₃and H₂O. The NH₃bending and weak-bond stretching force constants for CH₃CCH–NH₃are less than those found in NCCCH–NH₃, NCH–NH₃, and HCCH–NH₃, suggesting that the hydrogen bonding interaction is particularly weak in CH₃CCH–NH₃. The weakness of this hydrogen bond is partially a consequence of the orientation of the monomer electric dipole moments in the complex. In CH₃CCH–NH₃the antialigned monomer dipole moments lead to a repulsive dipole–dipole interaction energy, while in NCH–NH₃and NCCCH–NH₃the aligned dipoles give an attraction interaction.     

Vladimir Aleksandrovich Krasil’nikov (September 14, 1912–March 17, 2000)

Chronicle

Vladimir Aleksandrovich Krasil’nikov (September 14, 1912–March 17, 2000)     

Future conferences and symposia (October 2011–)

Events

Future conferences and symposia (October 2011–)     

In memory of A.M. Dykhne (October 27, 1933–January 6, 2005)

Chronicle

In memory of A.M. Dykhne (October 27, 1933–January 6, 2005)     

Sm3（F3,Co,Mn）29 compounds：promising materials for permanent magnets

The outstanding hard-magnetic properties are reported of Sm_3Fe_{28.1-x}Co_xMo_{0.9} compounds with x=12, 14, 16. In this alloy system, only a small amount of Mo is needed to stabilize the 3:29 structure so that the magnetic properties are not seriously affected by the presence of this nonmagnetic element. Substitution of Co for Fe leads to a significant increase of the magnetic anisotropy, and for x≥14 the easy magnetization direction changes from easy plane to the easy axis. In this alloy system, the compound Sm_3Fe_{12.1}Co_{16}Mo_{0.9} is a very promising candidate for permanent magnet applications. Its room temperature saturation magnetization (μ_0M_s=1.5 T) and anisotropy field (B_{an}=6.5 T) are comparable to the values for Nd_2Fe_{14}B (μ_0M_s=1.6 T and B_{an}=7 T). However, the Curie temperature of Sm_3Fe_{12.1}Co_{16}Mo_{0.9} is 1020 K, which is appreciably higher than that for Nd_2Fe_{14}B (T_C=588 K).     

In memory of Evgeniĭ L’vovich Shenderov (June 1, 1935–September 1, 2001)

Chronicle

In memory of Evgeni $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ L’vovich Shenderov (June 1, 1935–September 1, 2001)     

Chemical,magnetic and charge ordering in the system hematite–ilmenite,Fe2O3–FeTiO3

Spin polarized electronic structure calculations of total energies for ordered supercells in the system Fe₂O₃–FeTiO₃ suggest that some layered ordered phases are more stable than an isocompositional mechanical mixture of hematite, Fe₂O₃, and ilmenite, FeTiO₃. This result contradicts established ideas about hematite–ilmenite phase relations because it suggests that there is at least one stable ordered phase with a bulk composition intermediate between hematite and ilmenite. It is not clear if this result is an artifact of the approximations made in generalized gradient spin density functional calculations, or if an intermediate phase, or phases, is in fact stable. The electronic structure of a 30-atom layered supercell was studied by a variety of techniques. The supercell structure is FTFFFT, where F is an Fe layer and T is a Ti layer perpendicular to the hexagonal c axis. The idea was to investigate possible charge ordering on Fe sites, that is a postulate of the ‘lamellar magnetism hypothesis’, but significant Fe²⁺–Fe³⁺ordering is not predicted.