Valency

About: Valency is a research topic. Over the lifetime, 1632 publications have been published within this topic receiving 26141 citations.

Dimensional analysis of interstitial phases with the AlCr2C structure

Abstract: A dimensional analysis is reported of interstitial phases with the hexagonal AlCr2C, NM2C, structure, which is based on examining the variation of the unit-cell parameters a and c as functions of DM and DN, the diameters of the M and N components for CN 12. The observed behaviour is uniquely different to that of phases with all other structures so examined, there being a drastic change of the DN dependences of a and c in the region where a ≃ DN. Nevertheless, equations are derived which reproduce the a and c dependences on DM, DN and the valency of the M component to better than 0.5% and which indicate the atomic arrays that control the cell dimensions. It is found that the M-M distances that do not lie in (0001) planes and which form half of the sides of the M octahedra surrounding the metalloid atoms, are an invariant feature of the structure for phases with the same M component. This invariant distance couples a, c and z, the atomic parameters of the M atoms, and it causes e dependences on 6.5DN (a > DN) and -1.65DN (a < DN), which could not possibly arise through the intrinsic contacts of the N atoms. The electronic distribution from the M atoms to M-M and M-N contacts and also to bands derived from the metalloid 2p states and transition-metal d states, is further analysed to account for the apparent dependence of a and c on the M-atom valency. The cell dimensions of SnM2C phases with the AlCr2C structure do not follow the systematic variations discussed above; reasons are advanced for this.

Photoelectron diffraction for probing valency and magnetism of 4 f -based materials: A view on valence-fluctuating EuIr 2 Si 2

Abstract: We present and discuss the methodology for modeling $4f$ photoemission spectra, $4f$ photoelectron diffraction (PED) patterns, and magnetic dichroism effects for rare-earth-based materials. Using PED and magnetic dichroism in photoemission, we explore the electronic and magnetic properties of the near-surface region of the valence-fluctuating material ${\mathrm{EuIr}}_{2}{\mathrm{Si}}_{2}$. For the Eu-terminated surface, we found that the topmost Eu layer is divalent and exhibits a ferromagnetic order below 10 K. The valency of the next Eu layer, that is the fifth atomic layer, is about 2.8 at low temperature that is close to the valency in the bulk. The properties of the Si-terminated surface are drastically different. The first subsurface Eu layer (fourth atomic layer below the surface) behaves divalently and orders ferromagnetically below 48 K. Experimental data indicate, however, that there is an admixture of trivalent Eu in this layer, resulting in its valency of about 2.1. The next deeper lying Eu layer (eighth atomic layer below the surface) behaves mixed valently, but the estimated valency of 2.4 is notably lower than the value in the bulk. The presented approach and obtained results create a background for further studies of exotic surface properties of $4f$-based materials, and allow us to derive information related to valency and magnetism of individual rare-earth layers in a rather extended area near the surface.

The electron theory of metallic magnesium

Abstract: Results are given on the calculations of the energetic spectra of valency electrons in metallic magnesium according to the new method suggested by Z. Matyas and on the basis of group analysis of the wave functions of valency electrons in a crystal. The binding energy was calculated and an attempt was made to explain the spectral distribution of the soft X-ray emission spectrum. The author further attempted an explanation of the quantitative changes in the dependence of the lattice constant of some solid solutions of multivalent metals in magnesium. In all cases the agreement with experiment is satisfactory.