scholarly journals Off-Diagonal Induction of Short-Range Order: Spin Pair Correlation of the Quantum XXZ-Model

1988 ◽  
Vol 80 (4) ◽  
pp. 594-597 ◽  
Author(s):  
S. Homma ◽  
H. Matsuda ◽  
T. Horiki ◽  
N. Ogita
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
Xxz Model ◽  
Spin Pair

Pb()O3-type Perovskites: Part I. Pair-correlation Theory of Order-disorder Phase Transition

1997 ◽  
Vol 12 (8) ◽  
pp. 2117-2126 ◽  
Author(s):  
Hyun M. Jang ◽  
Su-Chan Kim
Keyword(s):  
Long Range ◽  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
Statistical Thermodynamic ◽  
Range Order Parameter ◽  
Long Range Order ◽  
Short Range Order Parameter

The limitation of the long-range order parameter and the necessity of the short-range order parameter for the thermodynamic description of Pb()O3-type perovskites are discussed. Based on the discussion, a statistical thermodynamic model that takes into account the configuration of the neighboring B-site ions (B′ and B″ cations) was developed. A pair-correlation approximation was used in the calculation of the configurational entropy and the long-range coulombic interaction energy between the nearest B-site ions. The theoretical calculations using Pb(Sc1/2Ta1/2)O3 (PST) and Pb(Sc1/2Nb1/2)O3 (PSN) systems indicate that the short-range order parameter persists over a wide range of temperatures examined (0–1800 K) and that there possibly occur consecutive long-range order-disorder transitions in the configuration of B-site cations. The possibility of the existence of short-range ordering above the long-range order-disorder transition temperature was also examined using the annealed PSN specimen as a typical example of Pb()O3-type perovskites.

Short Range Order in Structural Models for the Amorphous Fe80B20- and Ni81B19-Alloys

1988 ◽  
Vol 43 (12) ◽  
pp. 1047-1054 ◽  
Author(s):  
P. Kizler ◽  
P. Lamparter ◽  
S. Steeb
Keyword(s):  
Correlation Functions ◽  
Amorphous Alloys ◽  
Short Range ◽  
Short Range Order ◽  
Bond Angle ◽  
Pair Correlation ◽  
Structural Models ◽  
Range Order ◽  
Pair Correlation Functions

The short range order in several structural models for amorphous alloys is investigated with respect to pair correlation functions, bond angle distributions and other properties. Despite of the different principles of modelling, the topological short range order turned out to be almost identical. Therefore also the question for the triplet correlations to some extent is found solved. Remaining differences thus consist regarding more complex correlations among the atoms.

Structural Investigation of the Metallic Glasses Mg85.5Cu14.5 and Mg70Zn30

1983 ◽  
Vol 38 (2) ◽  
pp. 142-148 ◽  
Author(s):  
E. Nassif ◽  
P. Lamparter ◽  
W. Sperl ◽  
S. Steeb
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
Order Effects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Factors ◽  
Similar Chemical ◽  
Total Structure

Abstract The total structure factors as well as the total pair correlation functions for amorphous Mg85.5Cu14.5 (by neutron and X-ray diffraction) and for amorphous Mg70Zn30 (by X-ray diffraction) were determined. Both alloys show similar chemical short range order effects. From the total pair correlation function of the Mg85.5Cu14.5 glass, partial coordination numbers and atomic distances could be extracted. Comparison with the structure of crystalline Mg2Cu suggests that the short range order around the copper atoms is similar in the amorphous and the crystalline phase. The densities of both amorphous alloys were measured yielding negative excess volumina.

X-Ray Diffraction Study on the Structure of Molten MgxZn(100 -x)-Alloys

1987 ◽  
Vol 42 (5) ◽  
pp. 507-510 ◽  
Author(s):  
E. Bühler ◽  
P. Lamparter ◽  
S. Steeb
Keyword(s):  
Amorphous Alloy ◽  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nearest Neighbours ◽  
Total Structure Factor ◽  
Total Structure

By means of X-ray diffraction in transmission the molten MgxZn(1oo-x)-alloys (x = 0, 8, 15, 30, 40, 50, 60, 70, 73, 80, 90, 100) were investigated and the total structure factor S (Q) , the total pair correlation function, the number of nearest neighbours as well as the atomic distances were evaluated. For 30 ≦ x ≦ 80 a premaximum in S (Q) was observed which is caused by chemical short range order. The comparison of the premaximum of the Mg70Zn30-melt with that of the corresponding amorphous alloy shows that within the melt the chemical short range order amounts to about 40% of that of the amorphous alloy.

Influence of Hydrogen on the Structure of Amorphous Sputtered Fe-Co-Tb Films by Means of Wide- and Small Angle Neutron Scattering

1991 ◽  
Vol 46 (12) ◽  
pp. 1015-1020 ◽  
Author(s):  
M. Heckele ◽  
R. Bellissent ◽  
A. Brunseh ◽  
P. Lamparter ◽  
S. Steeb
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
Hydrogen Incorporation ◽  
Plane Anisotropy ◽  
The Individual

Abstract Sputtered amorphous Fe-Co Tb-films with perpendicular and in-plane magnetic anisotropy were investigated by wide- and small angle neutron scattering. By combination with X-ray data the maxima in the pair correlation function could be attributed to the individual atomic pairs. Thus also partial coordination numbers and a short range order parameter could be determined. Wide angle diffraction revealed that the film with magnetic in-plane anisotropy contained 13 atomic percent hydrogen. The hydrogen incorporation causes substantial changes in the short range order, associated with enhanced formation of Tb-rich clusters, and the in-plane anisotropy. The clustering effect was confirmed by results from small angle scattering with polarized neutrons

scholarly journals Short-Range Spin Pair Correlation in the One-Dimensional Quantum XXZ Model

1989 ◽  
Vol 82 (3) ◽  
pp. 507-513 ◽  
Author(s):  
Tsuyoshi Horiki ◽  
Shigeo Homma ◽  
Hirotsugu Matsuda ◽  
Naofumi Ogita
Keyword(s):  
Short Range ◽  
Pair Correlation ◽  
Xxz Model ◽  
One Dimensional ◽  
Spin Pair ◽  
The One

Model Calculations of the Structure of Ni-Nb Metallic Glasses

1995 ◽  
Vol 50 (4-5) ◽  
pp. 329-336 ◽  
Author(s):  
P. Lamparter
Keyword(s):  
Metallic Glasses ◽  
Short Range ◽  
Short Range Order ◽  
Computer Modelling ◽  
Pair Correlation ◽  
Range Order ◽  
Chemical Effect ◽  
Perfect Agreement ◽  
Model Calculations ◽  
The Impact

Abstract The partial pair correlation functions of amorphous NixNb100-x alloys (x = 40, 50, 56, and 63) were simulated by computer modelling. A Cluster Relaxation procedure yielded reasonable agree­ ment with the experimental functions when non-additive pair potentials with preference for Ni-Nb atomic pairs were applied. With the use of the Reverse Monte Carlo method perfect agreement could be achieved. The impact of the chemical effect on the short range order is discussed by comparison with a statistical reference cluster. The analysis of the model clusters showed that the chemical short range order effect in amorphous Ni-Nb alloys, increasing with the Ni concentration, does not in­ volve specific stereochemical atomic arrangements. There is no correspondence to the short range order in crystalline Ni3Nb. The structure of Ni-Nb metallic glasses can be described as a polytetra-hedral packing with preferred hetero-coordination.

First-Principles Calculations of Heusler Phase Precursors in the Atomic Short-Range Order of Disordered BCC Ternary Alloys

1995 ◽  
Vol 408 ◽  
Author(s):  
Jeffrey D. Althoff ◽  
Duane D. Johnson
Keyword(s):  
Transition Temperature ◽  
First Principles ◽  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
Ternary Alloys ◽  
First Principles Calculations ◽  
Effective Interactions ◽  
Special Points

AbstractWe apply our recently developed first-principles theory of atomic short-range order in disordered multicomponent alloys to CuAuZn2 and AgAuZn2, two alloys which display partially-ordered B2 phases as well as fully-ordered Heusler structures. The calculated Warren-Cowley pair correlation functions for both alloys peak at the special points 〈½ ½ ½〉 and 〈100〉, with the peak at 〈100〉 dominant. This is indicative of a tendency to B2 order at high temperatures, and a subsequent tendency to Heusler-type order at lower temperatures. An analysis in terms of effective interactions shows that the Au Zn interaction drives the 〈100〉 ordering tendency, while the Ag Au and Cu Au interactions contribute more to the 〈 ½ ½ ½〉ordering tendency - this effect is larger in CuAuZn2 and should lead to a slightly higher transition temperature for the B2 to Heusler transition in CuAuZn2 as compared to AgAuZn2.

Short-range order effects in amorphous FexSi1-x/Si multilayers induced by preparation conditions

1998 ◽  
Vol 08 (PR2) ◽  
pp. Pr2-175-Pr2-178 ◽  
Author(s):  
G. T. Pérez ◽  
F. H. Salas ◽  
R. Morales ◽  
L. M. Álvarez-Prado ◽  
J. M. Alameda
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Order Effects ◽  
Preparation Conditions
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