Thermal vacancy formation and positron–vacancy interaction in Ti3Al at high temperatures

1996 ◽  
Vol 80 (2) ◽  
pp. 724-728 ◽  
Author(s):  
R. Würschum ◽  
E. A. Kümmerle ◽  
K. Badura‐Gergen ◽  
A. Seeger ◽  
Ch. Herzig ◽  
...  
Keyword(s):  
High Temperatures ◽  
Vacancy Formation ◽  
Thermal Vacancy

Thermal vacancy formation enthalpy of random solid solutions: The FePt case

2018 ◽  
Vol 143 ◽  
pp. 206-211 ◽  
Author(s):  
H.B. Luo ◽  
Q.M. Hu ◽  
J. Du ◽  
A.R. Yan ◽  
J.P. Liu
Keyword(s):  
Solid Solutions ◽  
Formation Enthalpy ◽  
Vacancy Formation ◽  
Thermal Vacancy

Crystallization and Thermal Vacancy Formation in Fe73.5Si13,5B9Nb3Cu1 and Zr65Cu17.5Ni10Al7.5

1997 ◽  
Vol 255-257 ◽  
pp. 530-532 ◽  
Author(s):  
R. Dittmar ◽  
R. Würschum ◽  
W. Ulfer ◽  
Hans Eckhardt Schaefer
Keyword(s):  
Vacancy Formation ◽  
Thermal Vacancy

Thermal vacancy formation in Co-based Heusler-type alloys Co2MnZ (Z=Si, Ge, Sn)

2009 ◽  
Vol 480 (2) ◽  
pp. 462-468 ◽  
Author(s):  
M. Kogachi ◽  
S. Kikuchi ◽  
T. Fujiwara ◽  
F. Hori
Keyword(s):  
Vacancy Formation ◽  
Thermal Vacancy

Thermodynamics of Oxygen Chemistry on PbTiO3 and LaMnO3 (001) Surfaces

2011 ◽  
Vol 1309 ◽  
Author(s):  
Ghanshyam Pilania ◽  
R. Ramprasad
Keyword(s):  
Phase Diagram ◽  
High Temperatures ◽  
First Principles ◽  
Room Temperature ◽  
Oxidation Catalysis ◽  
Vacancy Formation ◽  
Surface Phase ◽  
Surface Phases ◽  
O Vacancy ◽  
Low Pressures

ABSTRACTWe present a first principles thermodynamic study of O ad-atom and vacancy formation on the AO- and BO2-terminated (001) surfaces of the PbTiO3 (PTO) and LaMnO3 (LMO) cubic perovskites. Our results show that, owing to the highly energetically unfavorable nature of O vacancy formation on these surfaces, O vacancies appear only at high temperatures and practically irrelevant low pressures on the (T, p) surface phase diagram. In contrast, effortless formation of O ad-atoms on the surfaces is encountered at practically achievable pressures and temperatures. Above room temperature and close to atmospheric pressures, we predict clean PbO and TiO2-terminated (001) PTO surfaces as the stable surface phases while partially or fully O ad-atom covered surfaces are found to be more stable for LMO. These results are consistent with the observation that LMO is far more active towards oxidation catalysis than PTO.

Lattice-Gas-Decomposition Model for Vacancy Formation Correlated with B2 Atomic Ordering in Intermetallics

2008 ◽  
Vol 1128 ◽  
Author(s):  
A. Biborski ◽  
L. Zosiak ◽  
R. Kozubski ◽  
V. Pierron-Bohnes
Keyword(s):  
Monte Carlo ◽  
Lattice Gas ◽  
Defect Formation ◽  
Vacancy Concentration ◽  
Kinetic Monte Carlo ◽  
Thermodynamic Formalism ◽  
Pair Interaction ◽  
Vacancy Formation ◽  
Atomic Ordering ◽  
Thermal Vacancy

AbstractThermal vacancy formation correlated with atomic ordering was modelled in B2-ordering A-B binary intermetallics. Ising Hamiltonian was implemented with a specific thermodynamic formalism for thermal vacancy formation based on the phase equilibria in a lattice gas composed of atoms and vacancies. Extensive calculations within the Bragg-Williams approximation [1] were followed by Semi-Grand Canonical Monte Carlo (SGCMC) simulations. It has been demonstrated that for the atomic pair-interaction energies favouring vacancy formation on A-atom sublattice, equilibrium concentrations of vacancies and antisite defects result mutually proportional in well defined temperature ranges. The effect observed both in stoichiometric and non-stoichiometric (both A-rich and B-rich) binary alloys was interpreted as a tendency for triple defect formation. In B-rich alloys vacancy concentration did not extrapolate to zero at 0 K, which indicated the formation of constitutional vacancies. Energetic conditions for the occurrence of the effects were analysed in detail. The modelled temperature dependence of vacancy concentration in the B2-ordering A-B binaries with triple defects will be included in the Kinetic Monte Carlo (KMC) simulations of chemical ordering kinetics in these systems with reference to the experimental results obtained for NiAl [2].

scholarly journals Thermal vacancy formation andD03ordering in nanocrystalline intermetallic(Fe3Si)95Nb5

2001 ◽  
Vol 63 (13) ◽  
Author(s):  
L. Pasquini ◽  
A. A. Rempel ◽  
R. Würschum ◽  
K. Reimann ◽  
M. A. Müller ◽  
...  
Keyword(s):  
Vacancy Formation ◽  
Thermal Vacancy

Atomic Defects in Intermetallic Compounds and Diffusion Processes

1998 ◽  
Vol 527 ◽  
Author(s):  
H.-E. Schaefer ◽  
K. Frenner ◽  
R. Würschum
Keyword(s):  
Transition Metal ◽  
Intermetallic Compounds ◽  
High Temperatures ◽  
Diffusion Processes ◽  
Formation Enthalpy ◽  
Length Change ◽  
Vacancy Formation ◽  
And Migration ◽  
Lifetime Studies ◽  
Metal Aluminides

ABSTRACTFor the understanding of the properties of the technically important intermetallic compounds as transition metal aluminides and silicides the understanding of atomic defect properties is pivotal. From recent positron lifetime studies high or low values for the effective vacancy formation enthalpy were found for close-packed or for more open-structured bcc type compounds, respectively, which can be well understood theoretically. In B2-FeAl the vacancy migration enthalpy could be additionally derived at high temperatures from vacancy equilibration processes. It is shown here by a study on B2-FeAl in comparison to the positron annihilation experiments that the thermal formation and migration of defects can be specifically investigated by time-dependent length-change experiments at high temperatures by the defect equilibration behavior after temperature changes. With the present data on vacancy formation and migration the wide variation of the transition-metal self-diffusivities in intermetallic compounds can be understood.

Sign in / Sign up

Export Citation Format

Share Document