Chemical Bonding, Point Defects and Positron Lifetimes in FeSi2 from First-Principles Calculations

2014 ◽  
pp. 303-323
Author(s):  
Masataka Mizuno ◽  
Hideki Araki
Keyword(s):  
Point Defects ◽  
Chemical Bonding ◽  
First Principles ◽  
First Principles Calculations ◽  
Positron Lifetimes

scholarly journals First Principles Calculations of Defects in Unstable Crystals: Austenitic Iron

2011 ◽  
Vol 1363 ◽  
Author(s):  
G.J. Ackland ◽  
T.P.C. Klaver ◽  
D.J. Hepburn
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Defect Formation ◽  
Single Layer ◽  
Temperature Limit ◽  
Reference State ◽  
First Principles Calculations ◽  
General Picture ◽  
Bcc Iron ◽  
Defect Energies

ABSTRACTFirst principles calculations have given a new insight into the energies of point defects in many different materials, information which cannot be readily obtained from experiment. Most such calculations are done at zero Kelvin, with the assumption that finite temperature effects on defect energies and barriers are small. In some materials, however, the stable crystal structure of interest is mechanically unstable at 0K. In such cases, alternate approaches are needed. Here we present results of first principles calculations of austenitic iron using the VASP code. We determine an appropriate reference state for collinear magnetism to be the antiferromagnetic (001) double-layer (AFM-d) which is both stable and lower in energy than other possible models for the low temperature limit of paramagnetic fcc iron. Another plausible reference state is the antiferromagnetic (001) single layer (AFM-1). We then consider the energetics of dissolving typical alloying impurities (Ni, Cr) in the materials, and their interaction with point defects typical of the irradiated environment. We show that the calculated defect formation energies have fairly high dependence on the reference state chosen: in some cases this is due to instability of the reference state, a problem which does not seem to apply to AFM-d and AFM-1. Furthermore, there is a correlation between local free volume magnetism and energetics. Despite this, a general picture emerge that point defects in austenitic iron have geometries similar to those in simpler, non-magnetic, thermodynamically stable FCC metals. The defect energies are similar to those in BCC iron. The effect of substitutional Ni and Cr on defect properties is weak, rarely more than tenths of eV, so it is unlikely that small amounts of Ni and Cr will have a significant effect on the radiation damage in austenitic iron at high temperatures.

scholarly journals Effect of point defects on the electronic density states of SnC nanosheets: First-principles calculations

2017 ◽  
Vol 7 ◽  
pp. 3209-3215 ◽  
Author(s):  
Soleyman Majidi ◽  
Amine Achour ◽  
D.P. Rai ◽  
Payman Nayebi ◽  
Shahram Solaymani ◽  
...  
Keyword(s):  
Point Defects ◽  
First Principles ◽  
First Principles Calculations ◽  
Electronic Density

Chromium point defects in hexagonalBaTiO3: A comparative study of first-principles calculations and experiments

2015 ◽  
Vol 91 (15) ◽  
Author(s):  
Sanjeev K. Nayak ◽  
Hans T. Langhammer ◽  
Waheed A. Adeagbo ◽  
Wolfram Hergert ◽  
Thomas Müller ◽  
...  
Keyword(s):  
Comparative Study ◽  
Point Defects ◽  
First Principles ◽  
First Principles Calculations

scholarly journals Positron Lifetimes in Solids from First Principles Calculations

1992 ◽  
Vol 105-110 ◽  
pp. 469-476 ◽  
Author(s):  
P.A. Sterne ◽  
J.H. Kaiser ◽  
J.C. O'Brien ◽  
Richard H. Howell
Keyword(s):  
First Principles ◽  
First Principles Calculations ◽  
Positron Lifetimes

scholarly journals Native point defects in CuIn1−xGaxSe2: hybrid density functional calculations predict the origin of p- and n-type conductivity

2014 ◽  
Vol 16 (40) ◽  
pp. 22299-22308 ◽  
Author(s):  
J. Bekaert ◽  
R. Saniz ◽  
B. Partoens ◽  
D. Lamoen
Keyword(s):  
Charge Carrier ◽  
Point Defects ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
First Principles Calculations ◽  
Photoluminescence Spectra ◽  
Type Conductivity ◽  
Native Point Defects ◽  
Hybrid Density Functional

Starting from first-principles calculations, many experimental observations such as photoluminescence spectra, charge carrier densities and freeze-out can be explained.

First-Principles Study on the Clean and Nb Doped TiO2(110)γ-TiAl(111) Interfaces

2012 ◽  
Vol 602-604 ◽  
pp. 555-558 ◽  
Author(s):  
Hui Nan Hao ◽  
Xu Wang ◽  
Fu He Wang
Keyword(s):  
Structural Stability ◽  
Density Of States ◽  
Chemical Bonding ◽  
First Principles ◽  
Adhesion Energy ◽  
First Principles Calculations ◽  
First Principles Study

In this paper, the structural stability, adhesion and chemical bonding of the TiO2 (110)/TiAl (111) interface are investigated by the first-principles calculations. We predict the maximum adhesion energy of 1.91J/m2 of the TiO2/TiAl interface. We also calculated the Nb doped interface, and found that the doped Nb atom prefers to replace the Ti atom at the second layer of TiAl slab. The atomic geometry and density of states are analyzed. The results show that the effect of doped Nb is localized and insignificant on the TiO2 (110)/TiAl(111) interface.

Unifying Chemical Bonding Models for Boranes

2007 ◽  
Vol 1038 ◽  
Author(s):  
Mao-Hua Du ◽  
Susumu Saito ◽  
S. B. Zhang
Keyword(s):  
Coordination Number ◽  
Triangular Lattice ◽  
Chemical Bonding ◽  
First Principles ◽  
First Principles Calculations ◽  
Cage Structure ◽  
Boron Hydrides

AbstractWe demonstrate, based on first-principles calculations, that chemical bonding in deltahedral boron hydrides, BnHn2− also known as closo boranes, can be understood within the three-center two-electron (3c2e) bonding model in line with other families of boranes. We show that bonding in the triangular lattice of BnHn2− cages can be described by delocalized resonant 3c2e bonding. We also find that the reason for all the BnHn2− to be dianions can be attributed to the reduction of boron coordination number in the deltahedral cage structure from that of boron sheet with triangular lattice.

First-principles calculations of point defects in inorganic nanotubes

2013 ◽  
Vol 250 (4) ◽  
pp. 793-800 ◽  
Author(s):  
Yuri F. Zhukovskii ◽  
Sergei Piskunov ◽  
Jevgenijs Begens ◽  
Jurijs Kazerovskis ◽  
Oleg Lisovski
Keyword(s):  
Point Defects ◽  
First Principles ◽  
First Principles Calculations ◽  
Inorganic Nanotubes
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