scholarly journals Bulk moduli of PbSxSe1−x, PbSxTe1−x and PbSexTe1−x from the combination of the cBΩ model with the modified Born theory compared to generalized gradient approximation

2016 ◽  
Vol 30 (34) ◽  
pp. 1650409 ◽  
Author(s):  
Nicholas V. Sarlis ◽  
Efthimios S. Skordas
Keyword(s):  
Satisfactory Agreement ◽  
Alternative Procedure ◽  
Generalized Gradient ◽  
Approximation Approach ◽  
Generalized Gradient Approximation ◽  
Text Model ◽  
Cbω Model ◽  
Thermodynamical Model

The bulk moduli of PbS[Formula: see text]Se[Formula: see text], PbS[Formula: see text]Te[Formula: see text] and PbSe[Formula: see text]Te[Formula: see text] have been recently determined by employing a thermodynamical model, the so-called [Formula: see text] model, which has been found to give successful results in several applications of defects in solids. Here, we suggest an alternative procedure for this determination which combines the [Formula: see text] model with the modified Born theory. The results are in satisfactory agreement with those deduced independently by the generalized gradient approximation approach.

Engineering the Topological Phase of Half Heusler Compounds by Computer

2015 ◽  
Vol 713-715 ◽  
pp. 2695-2698
Author(s):  
L.Y. Wang ◽  
S. Gao
Keyword(s):  
First Principles ◽  
Present Finding ◽  
Spin Orbit Coupling ◽  
Topological Phase ◽  
Heusler Compounds ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Approximation Approach ◽  
Generalized Gradient Approximation ◽  
Band Inversion

Band inversion mechanisms of half Heusler compouds XMBi (X=Sc, Y, Lu, La, M=Pd, Pt) is investigated under different conditions, based on first-principles calculations with generalized gradient approximation approach. The results shown that Spin-orbit coupling, however, is not the leading cause but an account can add further fuel to the band inversion. The present finding provides an effective scheme to search for topologically nontrivial materials.

scholarly journals Interconnection of defect entropies and enthalpies in BaF2 revisited

2016 ◽  
Vol 30 (06) ◽  
pp. 1650062 ◽  
Author(s):  
Efthimios S. Skordas
Keyword(s):  
Density Functional ◽  
Matrix Material ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Tetravalent Uranium ◽  
Generalized Gradient Approximation ◽  
And Migration ◽  
Bulk Elasticity ◽  
Thermodynamical Model ◽  
Expansivity Data

Here, we investigate the following key prediction of a thermodynamical model that interrelates the defect parameters with the bulk elastic and expansivity data: for various defect processes in a given matrix material, a proportionality exists between defect entropies and enthalpies. The investigation is focused on BaF2 for which ab initio calculations within density functional theory and the generalized-gradient approximation have been recently made as far as the formation and migration of intrinsic defects are concerned, as well as for the elastic constants. Four defect processes have been studied in BaF2: anion Frenkel formation, fluorine vacancy migration, fluorine interstitial motion and electrical relaxation associated with a single tetravalent uranium. For these processes, the entropies and enthalpies vary by almost two orders of magnitude and reveal a proportionality between them. We find that this proportionality is solely governed by the bulk elasticity and expansivity data, which conforms to the aforementioned thermodynamical model.

Interstitial vs. Substitutional Metal Insertion in V2O5 as Post-Lithium Ion Battery Cathode: A Comparative GGA/GGA+U Study with Localized Bases

2020 ◽  
Author(s):  
Daniel Koch ◽  
Sergei Manzhos
Keyword(s):  
Electronic Structure ◽  
Plane Wave ◽  
Transition Metal Oxides ◽  
Reasonable Agreement ◽  
Correction Term ◽  
Lithium Ion ◽  
Generalized Gradient ◽  
Main Group Metals ◽  
Generalized Gradient Approximation ◽  
Metal Insertion

<p></p><p>The generalized gradient approximation (GGA) often fails to correctly describe the electronic structure and thermochemistry of transition metal oxides and is commonly improved using an inexpensive correction term with a scaling parameter <i>U</i>. We tune <i>U</i> to reproduce experimental vanadium oxide redox energetics with a localized basis and a GGA functional. We find the value for <i>U</i> to be significantly lower than what is generally reported with plane-wave bases, with the uncorrected GGA results being in reasonable agreement with experiments. We use this computational setup to calculate interstitial and substitutional <a>insertion energies of main group metals in vanadium pentoxide</a> and find <a>interstitial doping to be thermodynamically favored</a>.</p><p></p>

Dissociation of dinitrogen on iron clusters: A detailed study of the Fe16 + N2 case.

2020 ◽  
Author(s):  
Bole Chen ◽  
Gennady L. Gutsev ◽  
Weiguo Sun ◽  
Xiao-Yu Kuang ◽  
Cheng Lu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Basis Set ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Iron Clusters ◽  
Generalized Gradient Approximation

The coalescence of two Fe8N as well as the structure of the Fe16N2 cluster were studied using density functional theory with the generalized gradient approximation and a basis set of...

Effect of Chromium and Vanadium on Nanolayered Ternary Carbides: AB Initio Study

2009 ◽  
Vol 609 ◽  
pp. 239-242
Author(s):  
A.E. Merad ◽  
M.B. Kanoun
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Ab Initio ◽  
Structural Parameters ◽  
Ab Initio Study ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Full Relaxation ◽  
Relaxation Procedure ◽  
Ternary Carbides

The Cr2AlC and V2AlC nanolayered ternary carbides are studied by performing APW-lo ab initio total energy calculations within the recent Wu-Cohen generalized gradient approximation GGA. Using full relaxation procedure of the volume and the atomic positions we obtained the structural parameters and electronic structure of the optimization hexagonal. Results were compared with the experimental ones. Interesting features are deduced. In fact, we have shown why these materials are conductors.

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