A Hybrid Open-Framework Aluminum Phosphate-Oxalate Possessing Large Circular 12-Membered Channels

A new aluminum phosphate-oxalate, I, [N₂C₄H₁₂]Al₂(PO₄) (HPO₄)(C₂O₄)]H₂O, has been synthesized hydrothermally in the presence of structure-directing amines. The hybrid structure comprises a vertex-linkage of AlO₆ octahedra, PO₄ tetrahedra, and C₂O₄ units leading to three-dimensional connectivity. The connectivity between AlO₆ and PO₄ units are such that it forms double-six rings that are connected to each other via the oxalate units, thereby leading to the formation of a large circular 12-membered channel of width 9 Å along the c axis. The structure-directing amine along with one water molecule is situated within this channel. The connectivity also forms two different types of 8-membered channels along the a and b axes. The three-dimensional structure of I, is very similar to the naturally occurring aluminosilicate zeolite, gmelinite. Crystal data for I are: monoclinic, space group Pccm, a=9.992(1), b=11.644(1), c=12.231(1) Å, V=1423.0(2), M=438.9, Z=4, R_F=0.07.     

The significance of the phase synthesis

This paper gives an account of the results of the tests that have been carried out to assess the relative importance of the phase angles and structure amplitudes in a Fourier synthesis. For this, the phase factors,e ^iα, have been combined in different ways with structure amplitudes such as when the latter are (a) replaced by the r.m.s. of the structure amplitudes (i.e., by √Σf _i ² ), (b) randomly chosen from the set of correct structure amplitudes, (c) made us much anti-correlated (about the mean) with the correct ones as possible and (d) taken to be those of an entirely different structure. The above syntheses which are only modifications of the phase synthesis,e ^iα , have been tested on both the centrosymmetric and non-centrosymmetric projections of a known structure. They strongly establish the greater importance of the phase angles in a Fourier synthesis.     

Multiple processes in electron-photon cascades

Recent experiments on high energy electron-photon cascades suggest the possibility of the following multiple processes:—

1. (i)
   Electron scattering with pair creation,     

A note on the ultraspherical polynomial approximation method of averaging

The method of averaging based on ultraspherical polynomial approximation has been applied to several non-linear oscillation problems. In this paper it is shown that the above method can be interpreted as a Galerkin technique with an appropriate weight function. Even though the analysis is not rigorous enough mathematically, it does provide insight into this generalized method of averaging.     

Sulphate ion dynamics in α-alums studied by esr at high pressures

The variation of zero-field splitting and linewidth of Cr³⁺ ion in KCr and KAI alums with hydrostatic pressure and with temperature is investigated. A model for the apparent phase transition is proposed on the basis of the reorientational motion of the SO^2?₄ groups.     

Detection of phase transitions in heavy silane by i.r. spectroscopy

An i.r. spectroscopic study of SiHD₃ isolated in SiD₄ reveals an apparent second-order phase transition at 38 K. In the lowest-temperature phase the SiD₄ molecules probably occupy two sites of C₁ symmetry. Between 38 K and 67 K the SiD₄ molecules probably occupy one site of C_s symmetry.