Nonstoichiometry, Defect Structure and Energetics in T (La2MO4; M=Cu, Ni) and T′ (Nd2CuO4) Structures

1990 ◽  
Vol 209 ◽  
Author(s):  
Anurag Dwivedi ◽  
A. N. Cormack
Keyword(s):  
Computer Simulation ◽  
Defect Structure ◽  
Interstitial Site ◽  
Intrinsic Defect ◽  
Oxygen Interstitial ◽  
Superconducting Compound ◽  
Metal Vacancies ◽  
Spontaneous Oxidation ◽  
Atomistic Computer Simulation

ABSTRACTAtomistic computer simulation is performed to investigate the extent and nature of nonstoichiometry in La2CuO4, and La2NiO4. Results suggest anion Frenkel to be the dominant intrinsic defect in both compounds. Spontaneous oxidation is predicted for La2NiO4 but not for La2CuO4; however, both compounds are more easily oxidised than reduced, as opposed to Nd2CuO4, a superconducting compound with same generic formula. Oxidation takes place via accommodation of oxygen interstitials; however, the possibility of metal vacancies can not be completely ignored in La2CuO4. There is only one favorable oxygen interstitial site which is same in both the compounds La2MO4 (M=Cu, Ni). We found a favorable oxygen interstitial site in T′ structure too. Relaxed structures around an oxygen interstitial in these compounds are reported.

Atomistic Computer Simulation of Alloy Corrosion

2009 ◽  
pp. 17-17-11
Author(s):  
RC Newman ◽  
Q Song ◽  
RA Cottis ◽  
K Sieradzki
Keyword(s):  
Computer Simulation ◽  
Atomistic Computer Simulation

Identification of ZnO Defect Structure by PL Spectroscopy

2011 ◽  
Vol 393-395 ◽  
pp. 135-138 ◽  
Author(s):  
Peng Fei Cheng ◽  
Han Chen Liu ◽  
Ying Tang Zhang
Keyword(s):  
Defect Structure ◽  
Sol Gel ◽  
Optoelectronic Devices ◽  
Good Deal ◽  
Intrinsic Defect ◽  
Zno Film ◽  
Gel Method ◽  
Zno Crystal ◽  
Almost All ◽  
Intrinsic Defect Structure

Defect structure of ZnO determines the optoelectronic characteristics of ZnO crystal and film. The identification and modulation of the defect structure is the foundation of the manufacture of optoelectronic devices. Although a good deal of research has been carried out about intrinsic defects and doping defects in ZnO, it is difficult to obtain a conclusive result accepted by all. In the paper, ZnO film is prepared by sol-gel method and the defect structure is expressed by photoluminescent (PL) spectroscopy. Based on some basic rules the intrinsic defect structure of ZnO is confirmed and the interaction of impurity Li and intrinsic defect is discussed. At the same time, some new electronic levels are proposed. It is surprising that although there are fourteen peaks in PL spectra of ZnO film, almost all the peaks can be identified by these basic rules.

The Defect Structure of Yttria Stabilized Zirconia

1985 ◽  
Vol 60 ◽  
Author(s):  
C.R.A. Catlow ◽  
A.V. Chadwick ◽  
A.N. Cormack ◽  
G.N. Greaves ◽  
M. Leslie ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Defect Structure ◽  
Yttria Stabilized Zirconia ◽  
Simulation Studies ◽  
Stabilized Zirconia ◽  
Association Models ◽  
Computer Simulation Studies

AbstractWe present results of EXAFS and computer simulation studies of the defect structure of yttria-stabilised zirconia. The results are analysed in terms of dopant-vacancy association models for this phase.

An Atomistic Computer Simulation of Crack Extension in Cubic Silicon Carbide

1992 ◽  
Vol 278 ◽  
Author(s):  
Akitaka Sawamura ◽  
Yoichi Watanabe ◽  
Ryoichi Yamamoto
Keyword(s):  
Stress Intensity Factor ◽  
Computer Simulation ◽  
Silicon Carbide ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Main Crack ◽  
Crack Extension ◽  
Crack Tip ◽  
Cubic Silicon Carbide ◽  
Atomistic Computer Simulation

AbstructAn atomistic computer simulation of mode I crack extension in cubic silicon carbide has been performed using a realistic many–body interatomic potential computed by Tersoff. The crack front is parallel to the [110] direction and the crack plane lies in the (111) plane. The stable crack tip configurations were calculated and the effective stress intensity factor and the effective crack tip position were evaluated in the relaxed atomic configuration by the least-square method. The crack was stable over a wide range of the stress intensity factors from 0. 6KG to 3. 4KG, where KG is the Griffith critical stress intensity factor. At 3.5KG an interatomic bond near the tip across the (001) plane ruptured and the crack advanced. When the crack is stable, the effective K is larger than the given K by nearly 0. 2KG to 0.4KG. Crack tip process was also simulated over a range of temperatures. At 1000K. secondary cracks were nucleated and grew like voids around the main crack, and thus the main crack was blunted.

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