The structure of a multilayer of lead stearate

Abstract

A study has been made of the molecular and crystallographic structures of Langmuir-Blodgett multilayer films of lead stearate. Electron microscopy and diffraction were used in the examination of such a film which had separated from the glass slide on which it had been formed. The films consist of a large number of three-dimensionally ordered lead stearate crystals arranged in near-perfect alignment, with the longest axes of their unit cell projecting from the plane of the supporting substrate. The unit cell of the lead stearate crystal is either monoclinic with the space group P21/a or orthorhombic with the space group P21212. The former is considered to be rather the more likely. The major lattice spacings are 4.96/~ (100), 7.38/~ (010) and 47 ~ (001). The/~ angle of the monoclinic unit cell is not known but is probably within a few degrees of 90 °. The lead atoms are in special positions in the basal plane, regardless of which is the correct unit cell, and the hydrocarbon chains make an angle of 62 + 5 ° with the basal plane. Any free stearic acid in the films occurs as a separate phase.

Electron Diffraction of Wet Phospholipid Bilayers

“…These features distinguish the pattern from that caused by an orthogonal packing which also has an apparent hexagonal symmetry (6). Many records show in addition a second order hexagonal pattern with the arcs rotated 7r/6 from those of the first order.…”

“…By applying selective area diffraction technique, an area as small as several square um may be sampled, thus enabling microscopic heterogeneities such as domain structures to be detected. This technique has been applied to study the dried monolayer deposits of fatty acids (6)(7)(8). The development of environmental chambers for electron microscopes (9) enables electron diffraction of molecular bilayers to be carried out under controlled hydration and temperature.…”

Quantitative study of irradiation damage in organo-metallic colloidal particles

“…Its formula is: (RCOO)2 Pb, (Pb0)o,5. The structure of the reverse micelles obtained has been described in previous papers [12,13] and can be assimilated to small fraction of Langmuir film dispersed in the solvent; each micellar particle has a size in the range 10-15 Â.…”

Zirconium–aluminium ordering in Zr5Ni4Al—a new superstructure in the family of U3Si2 related intermetallics

“…The Guinier pattern indicated that the crystal structure of Zr 5 Ni 4 Al is closely related to the family of tetragonal U 3 Si 2 intermetallics [21,22], and numerous additional reflections confirmed the doubling of the c parameter as required for the Zr 3 Al 2 [23] [19] with consideration of anisotropic microstrain broadening [20]. c Legendre polynoms.…”

“…A final difference Fourier synthesis revealed no significant residual peaks (see Table 1). The [19,20,23]. Table 3 Refined atomic positions and displacement parameters (pm 2 ) of ordered (P4 2 /m) and disordered (P4 2 /mnm) Zr 5 Ni 4 Al.…”