No abstract

Electron diffraction was used to study the stoichiometric dependence of the modulation wave vector in the incommensurately modulated structures of -and -Li x V 2 O 5 . For -Li x V 2 O 5 (0.32 x 0.52) and -Li x V 2 O 5 (0.52 x 0.80) the space group of the basic structure is P mmn, and the superspace group characterizing the one-dimensionally modulated structure is found to be P mmn (0 γ 1/2). The stoichiometry dependence of the modulation wave vector q can be described by a staircase function, with γ being constant at γ = 0.435(5) for -Li x V 2 O 5 . A second plateau has been observed in the stability field of -Li x V 2 O 5 for 0.550 x 0.575 with γ = 0.465(5). For the stoichiometry range 0.575 x 0.707, γ varies continuously between γ = 0.465(5) and γ = 0.565(5).In the present paper we will show that the system Li x V 2 O 5 can be described by an extended Frenkel-Kontorova model. Despite its extreme simplicity in the one-dimensional case, the model exhibits most of the features necessary for understanding the variation of the dependence of the modulation wave vector on the lithium stoichiometry.

No abstract

No abstract

Electron current in excess of the ideal square law occurred in p+-~-Al diodes and was interpreted in terms of double injection mechanism. The drain (Al) potential steps and the Richardson constants for electrons and for holes were determined using the excess electron current, and found to be 4nZ0.504 eV, Rn z 461 A cm-2 K-2 and $p z 0.61 6 eV, RI, z 93 A cm-2 K-2 respectively.