Energy dependence of the optical potential

It is important to take into account the intrinsic energy dependence of the optical potential arising from the energy dependence of the separation distance of the two-body effective interactions, used for calculating the optical potential. The consequence of such an energy dependence both for the direct and the exchange term is discussed.     

Contours pattern in LiIO3 crystal using ruby laser

Contours pattern due to second harmonic generation has been recorded successfully in the nonlinear crystal of LiIO₃ using a partially focused ruby laser beam as the fundamental radiations. The result is verified theoretically.     

Determination of sulphur functions with iodoso-compounds

Iodoso derivatives, e.g., m- and p-chlorophenyl, m- and p-methylphenyl and p-nitrophenyl-iodosoacetates and o-diacetoxyiodobenzoate, have been thoroughly investigated as oxidants and are proposed as analytical reagents for the determination of thiols, thioureas, isothiocyanates, organic sulphides, disulphides, xanthates, dithiocarbamates, amines and alcohols in aqueous and non-aqueous (acetic acid, acetonitrile, dimethylformamide) media. The error of the determination of thiols is 0.2% thioureas 0.5%, organic sulphides and disulphides 0.4%, isothiocyanates 0.4%, dithiocarbamates 0.4%, and xanthates 0.5%. All the methods are precise to 0.2-0.5%. It is also shown that the properties of the o-derivatives differ markedly from those of the m- and p-derivatives. The o-derivatives contain a 1-substituted 1,2-benzoiodoxilin-3-one ring system. The stability of this system is apparently associated with the size of the five-membered ring; other compounds in which iodine is apparently part of larger rings are less stable. o-Diacetoxyiodobenzoate appears to be the best analytical reagent of the iodoso series. The m- and p-iodosobenzoates are found unsuitable for quantitative oxidation of cysteine.     

Theory of the vibrational spectra of transition h.c.p. metals

Summary A semi-first principle (SFM) model using the concept of a rigid-shell moving relative to its nucleus to simulate the response of thed-electrons has been proposed for studying lattice dynamics of transition metals which belong to the h.c.p. structure. The long-range interaction between ion-ion as well as shell-shell via conduction electrons is described using the screened potential and the short-range interaction is described using two-body and three-body unpaired forces between cores as well as shells. Elastic constants, phonon dispersion curves and thermal properties,e.g. lattice specific heat, Debye characteristic temperature of three prominent transition metals (Zr, Hf, Ti) have been calculated and compared with the experimental results.

---

Riassunto Un modello a principio semiprimo (SFM) che usa il concetto di uno strato rigido con movimento relativo al suo nucleo per simulare la risposta degli elettronid è stato proposto per studiare la dinamica reticolare dei metalli di transizione che appartengono alla struttura h.c.p. Si descrive l’interazione a lungo raggio tra ione-ione e strato-strato via elettroni di conduzione usando il potenziale schermato e l’interazione a corto raggio è descritta usando forze spaiate a due e tre corpi tra i nuclei e gli strati. Sono state calcolate e confrontate con i risultati sperimentali le curve di dispersione dei fononi con costanti elastiche e le proprietà termiche, cioè calore specifico del fononi con costanti elastiche e le proprietà termiche, cioè calore specifico del reticolo, la temperatura caratteristica di Debye di tre importanti metalli di transizione (Zr, Hf, Ti).

---

Резюме Для исследования динамики решетки переходных металлов, которые имеют гексагональную с плотной упаковкой структуру, предлагается модель, использующая концепцию жесткой оболочки, движущейся относительно ее ядра, чтобы смоделировать откликd-электронов. Описывается длиннодействующее взаимодействие между ионами, а также между оболочками через электроны проводимости, используя экранированный потенциал. Короткодействующее взаимодействие описывается с помощью двух-частичных и трех-частичных неспаренных сил между остовами и оболочками. Вычисляются упругие постоянные, фононные дисперсионные кривые и тепловые свойства, т.е. удельная теплоемкость решетки, характеристическая температура Дебая для трех переходных металлов решетки, характеристическая температура Дебая для трех переходных металлов (Zr, Hf, Ti). Полученные результаты сравниваются с экспериментальными данными.

     

Studies on the valence electronic structure of Fe and Ni in Fe x Ni1−x alloys

K _β-to-K _α X-ray intensity ratios of Fe and Ni in pure metals and in Fe _x Ni_1−x alloys (x=0.20, 0.50, 0.58) exhibiting similar crystalline structure have been measured following excitation by 59.54 keV γ-rays from a ²⁴¹Am point source, to understand as to why the properties of permalloy Fe_0.2Ni_0.8 is distinct from other alloy compositions. It is observed that the valence electronic structure of Fe_0.2Ni_0.8 alloy is totally different from other alloys which may be attributed to its special magnetic properties.     

Mössbauer study of the modified pyrochlores CsMFeF6 (M = Mn,Ni)

⁵⁷Fe Mössbauer spectra of the modified pyrochlores CsMFeF₆ (M = Mn, Ni) were obtained between 1.5 K and room temperature. The spectra for single crystal and powder absorbers are very similar, and demonstrate the randomness associated with the iron sites. Nevertheless, the presence of two distinct iron sites, recently reported by Varret and Courbion for powder samples, is confirmed. Both CsMnFeF₆ and CsNiFeF₆ are antiferromagnets with Néel temperatures, T_N, of 25 and 5.2 K, respectively. The hyperfine fields lie on the Brillouin function with $\text{S =}\text{5}\text{2}$. The hyperfine parameters show that the iron ions are ferric in the high-spin state.     

The effect of defects on phonon scattering in YIG

Effect of different form of defects on phonon scattering in YIG have been studied. It has been found that defects in form of continuous lines behave like internal crystallite boundaries while weak sheet of defects scatter phonon like dislocations.     

517—π-Acid effect on electrode behaviour of ternary complexes in solution: Complex formation between copper(II)-1,10-phenanthroline complex and ligands containing oxygen and/or nitrogen donor atoms as secondary ligands. Part I

The mixed-ligand complexes, [Cu_x,(phen)_yL_z] (where phen stands for 1,10-phenanthroline and L for some aliphatic acids, aromatic acids, amino acids, phenols and ethylenediamine in the ratio 1 : 1 : 1 and 1 : 2 : 1) undergo two-step, diffusion-controlled, irreversible electro-reduction in 0.5 M KNO₃ at the dropping mercury electrode. The double-wave nature of these complexes may be attributed to the adsorption effect of 1,10-phenanthroline. From the characteristics of the irreversible wave, the rate constant k_f, for each complex has been calculated at its formal potential. The driving force for the formation of ternary systems has been analysed. The parent complex, [Cu(phen)] is found to show a discriminating nature towards the incoming secondary ligand. Additional stability effects compared to such systems with 2,2′-bipyridyl as the parent ligand have been explained on the basis of comparatively greater π-effects of 1,10-phenanthroline. Such effects are found t o become more pronounced, due to the cooperative effect, if the secondary ligand also has a π-system.