scholarly journals Evolutionary search for new high-kdielectric materials: methodology and applications to hafnia-based oxides

2014 ◽  
Vol 70 (2) ◽  
pp. 76-84 ◽  
Author(s):  
Qingfeng Zeng ◽  
Artem R. Oganov ◽  
Andriy O. Lyakhov ◽  
Congwei Xie ◽  
Xiaodong Zhang ◽  
...  
Keyword(s):  
First Principles ◽  
Fitness Function ◽  
Dielectric Materials ◽  
Breakdown Field ◽  
First Principles Calculations ◽  
Gate Oxides ◽  
Coordination Polyhedra ◽  
High Fitness ◽  
Speed Up ◽  
Computational Discovery

High-kdielectric materials are important as gate oxides in microelectronics and as potential dielectrics for capacitors. In order to enable computational discovery of novel high-kdielectric materials, we propose a fitness model (energy storage density) that includes the dielectric constant, bandgap, and intrinsic breakdown field. This model, used as a fitness function in conjunction with first-principles calculations and the global optimization evolutionary algorithm USPEX, efficiently leads to practically important results. We found a number of high-fitness structures of SiO2and HfO2, some of which correspond to known phases and some of which are new. The results allow us to propose characteristics (genes) common to high-fitness structures – these are the coordination polyhedra and their degree of distortion. Our variable-composition searches in the HfO2–SiO2system uncovered several high-fitness states. This hybrid algorithm opens up a new avenue for discovering novel high-kdielectrics with both fixed and variable compositions, and will speed up the process of materials discovery.

scholarly journals Simple and efficient way of speeding up transmission calculations with k-point sampling

2015 ◽  
Vol 6 ◽  
pp. 1603-1608 ◽  
Author(s):  
Jesper Toft Falkenberg ◽  
Mads Brandbyge
Keyword(s):  
First Principles ◽  
Periodic Boundary ◽  
Periodic Boundary Conditions ◽  
Phonon Transport ◽  
First Principles Calculations ◽  
Processing Scheme ◽  
Order Of Magnitude ◽  
Speed Up ◽  
Average Transmission ◽  
Graphene Structures

The transmissions as functions of energy are central for electron or phonon transport in the Landauer transport picture. We suggest a simple and computationally “cheap” post-processing scheme to interpolate transmission functions over k-points to get smooth well-converged average transmission functions. This is relevant for data obtained using typical “expensive” first principles calculations where the leads/electrodes are described by periodic boundary conditions. We show examples of transport in graphene structures where a speed-up of an order of magnitude is easily obtained.

scholarly journals The Verification of Thermoelectric Performance Obtained by High-Throughput Calculations: The Case of GeS2 Monolayer From First-Principles Calculations

2021 ◽  
Vol 8 ◽  
Author(s):  
Xiaolian Wang ◽  
Wei Feng ◽  
Chen Shen ◽  
Zhehao Sun ◽  
Hangbo Qi ◽  
...  
Keyword(s):  
Transport Properties ◽  
High Throughput ◽  
First Principles ◽  
Thermal Transport ◽  
Electrical Transport ◽  
Fitness Function ◽  
Industrial Applications ◽  
First Principles Calculations ◽  
Electrical Transport Properties ◽  
Thermal Transport Properties

Electronic fitness function (EFF, achieved by the electrical transport properties) as a new quantity to estimate thermoelectric (TE) performance of semiconductor crystals is usually used for screening novel TE materials. In recent years, because of the high EFF values, an increasing number of two-dimensional materials have been predicted to have the potential for TE applications via high-throughput calculations. Among them, the GeS2 monolayer has many interesting physical properties and is being used for industrial applications. Hence, in this work, we systematically investigated the TE performance, including both electronic and thermal transport properties, of the GeS2 monolayer with first-principles calculations. The results show that the structure of the GeS2 monolayer at 700 K is thermally unstable, so we study its TE performance only at 300 and 500 K. As compared with other typical TE monolayers, the GeS2 monolayer exhibits excellent electronic transport properties but a relatively high lattice thermal conductivity of 5.71 W m−1 K−1 at 500 K, and thus an unsatisfactory ZT value of 0.23. Such a low ZT value indicates that it is necessary to consider not only the electron transport properties but also the thermal transport properties to screen the thermoelectric materials with excellent performance through high-throughput calculations.

Electronic Structure and X-ray Absorption Spectra of Rutile TiO2 Using First-Principles Calculations

2014 ◽  
Vol 52 (12) ◽  
pp. 1025-1029
Author(s):  
Min-Wook Oh ◽  
Tae-Gu Kang ◽  
Byungki Ryu ◽  
Ji Eun Lee ◽  
Sung-Jae Joo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Absorption Spectra ◽  
First Principles ◽  
First Principles Calculations ◽  
Rutile Tio2 ◽  
X Ray ◽  
X Ray Absorption

To Bend or Not to Bend, the Dilemma of Multiple Bonds

2019 ◽  
Author(s):  
Michele Pizzocchero ◽  
Matteo Bonfanti ◽  
Rocco Martinazzo
Keyword(s):  
First Principles ◽  
2D Materials ◽  
Main Group ◽  
First Principles Calculations ◽  
Group 14 ◽  
Multiple Bonds ◽  
Main Group Elements ◽  
Structural Distortions

The manuscript addresses the issue of the structural distortions occurring at multiple bonds between high main group elements, focusing on group 14. These distortions are known as trans-bending in silenes, disilenes and higher group analogues, and buckling in 2D materials likes silicene and germanene. A simple but correlated \sigma + \pi model is developed and validated with first-principles calculations, and used to explain the different behaviour of second- and higher- row elements.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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