scholarly journals Ab initio calculation of field emission from metal surfaces with atomic-scale defects

2019 ◽  
Vol 100 (16) ◽  
Author(s):  
H. Toijala ◽  
K. Eimre ◽  
A. Kyritsakis ◽  
V. Zadin ◽  
F. Djurabekova
Keyword(s):  
Ab Initio ◽  
Field Emission ◽  
Ab Initio Calculation ◽  
Metal Surfaces ◽  
Atomic Scale

scholarly journals Examination of permittivity for depolarization field of ferroelectric by ab initio calculation, suggesting hidden mechanisms

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yukio Watanabe
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Spontaneous Polarization ◽  
Ab Initio Calculation ◽  
Surface Effects ◽  
Atomic Scale ◽  
Free Standing ◽  
Unit Cells ◽  
Scale Surface

AbstractElectrostatics of depolarization field Ed in relation to the polarization is studied. In particular, the value of permittivity for Ed (εd) in prototypical situations of ferroelectrics, including Mehta formula, is examined by ab initio calculations. By using spontaneous polarization PS corresponding to accurate experiment ones, we show εd = 1, which suggests that the results of εd ≫ 1 indicate hidden mechanisms; εd = 1 suggests that the effect of Ed is significant to induce intriguing important phenomena overlooked by εd ≫ 1. A bridge between εd = 1 and εd ≫ 1, i.e. the consistency of εd = 1 with conventional results is presented. The exact electrostatic equality of head-to-head–tail-to-tail domains to free-standing ferroelectrics is deduced. Hence, most stoichiometric clean freestanding monodomain ferroelectrics and head-to-head–tail-to-tail domains are shown unstable regardless of size, unless partially metallic. This verifies the previous results in a transparent manner. This conclusion is shown consistent with a recent hyperferroelectric LiBeSb and “freestanding” monolayer ferroelectrics, of which origin is suggested to be adsorbates. In addition, this restriction is suggested to break in externally strained ultrathin ferroelectrics. The macroscopic formulas of Ed are found valid down to a several unit-cells, when electronic and atomic-scale surface effects are unimportant and accurate PS is used.

AB INITIO CALCULATION OF NH3 SPECTRUM

2016 ◽  
Author(s):  
Oleg Polyansky ◽  
Nikolay Zobov ◽  
Andrey Yachmenev ◽  
Sergei Yurchenko ◽  
Jonathan Tennyson ◽  
...  
Keyword(s):  
Ab Initio ◽  
Ab Initio Calculation

Atomic and Electronic Structure of Boron-Doped Diamond Grain Boundaries Studied by Arhvtem and ab-Initio Calculation

2003 ◽  
Vol 764 ◽  
Author(s):  
Hiroyuki Togawa ◽  
Hideki Ichinose
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Ab Initio Calculation ◽  
Structure Model ◽  
Boron Doped Diamond ◽  
Boron Doped ◽  
Transmission Electron ◽  
Diamond Grain ◽  
Electron Energy Loss ◽  
Atomic And Electronic Structure

AbstractAtomic resolution high-voltage transmission electron microscopy and electron energy loss spectroscopy were performed on grain boundaries of boron-doped diamond, cooperated with the ab-initio calculation. Segregated boron in the {112}∑3 boundary was caught by the EELS spectra. The change in atomic structure of the segregated boundary was successfully observed from the image by ARHVTEM. Based on the ARHVTEM image, a segregted structure model was proposed.

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