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1
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Lattice Site Occupancy in Ternary Ordered Ni_{3}Al_{1-x}Fe_{x} Alloys Estimated by EXAFS

100%
Ławniczak-Jabłońska K., Pascarelli S., Boscherini F., Kozubski R.
Acta Physica Polonica A
|
1992
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vol. 82
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issue 2
315-322
EN
Extended X-ray absorption fine structure (EXAFS) spectroscopy offers additional experimental evidence to the solution of site occupancy problem in ternary NiAlX alloys. A study of local order in the stoichiometric Ni_{3}Al_{1-x}Fe_{x} ternary alloys (x = 0.02, 0.05, 0.10, 0.15, and 0.25) by EXAFS at the K-edge of Fe in the energy range from 7000 eV to 7600 eV are presented. Three models of substitutional behavior are considered - the preferential substitution of Fe atoms in: 1) Ni sites, 2) Al sites, 3) both sites. Data analysis was performed with theoretical and experimentally determined scattered photoelectron phases and amplitudes. The results of the EXAFS analysis are consistent with the picture in which most of the Fe atoms substitute Al sites and less than 25% of Fe atoms substitute Ni sites. Alloys with more than 10 at% of Fe showed higher tendency for ordering than those containing less than 10 at% Fe.
2
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Extended X-Ray Absorption Fine Structure Evidence for Homopolar Bonding in Amorphous Cd-As and Zn-P

80%
Burian A.
Acta Physica Polonica A
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1992
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vol. 82
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issue 2
309-313
EN
Local atomic arrangement in evaporated amorphous Cd-As and Zn-P films was investigated by extended X-ray absorption fine structure. Results of modelling indicate that bonds between atoms of the same kind occur for both (Cd,Zn)-rich and (As,P)-rich compositional regions. This specific chemical ordering, much alike to that in the corresponding crystalline polymorphs, appears to play a predominant role in determining of the local structures in these materials.
3
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Coadsorption of Beryllium and Potassium on a (001) Tungsten Plane

80%
Dworecki Z.
Acta Physica Polonica A
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1992
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vol. 81
|
issue 1
125-129
EN
The adsorption and coadsorption of beryllium and potassium on the tungsten (001) plane was studied using a probe-hole field electron microscope (FEM). Measurements were made at 78 K for potassium and at 300 K for beryllium. It has been found that the adsorption of potassium decreases and that of beryllium increases the work function of the W(001) plane. At small coverages with potassium atoms (θ_{k} < 0.2) on the W(001) plane successive evaporation of beryllium atoms causes a decrease of the work function. At larger coverages with potassium atoms an opposite effect is observed. An attempt has been made to compare the experimental results with the theoretical models suggested recently.
4
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Thermodynamic Stability of Two Rhombohedral Phases of Si_{0.5}Ge_{0.5} Alloy

80%
Bogusławski P.
Acta Physica Polonica A
|
1991
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vol. 80
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issue 2
299-302
EN
Thermodynamic stability of two ordered phases, RS1 and RS2, of Si_{0.5}Ge_{0.5} alloy is considered. Bulk and surface formation enthalpies are calculated using the model Tersoff's potential. RS2 structure is unstable, but its (001) ordered surface is stable against segregation. Properties of RS1 are just the opposite.
5
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Surface Stability of Ordered Ga_{0.5}In_{0.5}P and GaAs_{0.5}Sb_{0.5} Alloys

80%
Bogusławski P.
Acta Physica Polonica A
|
1991
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vol. 79
|
issue 1
125-128
EN
Formation enthalpies of (001) surfaces terminating ordered Ga_{0.5}In_{0.5}P and GaAs_{0.5}Sb_{0.5} alloys were calculated using the VFF model. For several ordered phases, chemically ordered surfaces were found to be stable against surface segregation. In particular, even phases unstable against bulk segregation may be terminated by a stable surface.
6
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Precipitates in Cd_{1-x}Ni_{x}Se Crystals Grown by the Bridgman Method

80%
Kachniarz J., Dynowska E., Miotkowska S., Paszkowicz W., Miotkowski I., Ramdas A.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
725-728
EN
Single crystals of Cd_{1-x}Ni_{x}Se alloys (x ranging from 0 to 0.075) were investigated using electron microprobe and X-ray diffraction. The analysis shows the presence of Ni-Se precipitates. The solubility limit of Ni is estimated to be 0.008.
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