Time-Dependent Density Functional Calculations on Hydrogenated Silicon Carbide Nanocrystals

2011 ◽  
Vol 679-680 ◽  
pp. 516-519 ◽  
Author(s):  
Marton Vörös ◽  
Peter Deák ◽  
Thomas Frauenheim ◽  
Adam Gali
Keyword(s):  
Silicon Carbide ◽  
Absorption Spectrum ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Time Dependent ◽  
First Principles Calculations ◽  
Hydrogenated Silicon ◽  
Reconstructed Surface ◽  
Dependent Density

The electronic structure and absorption spectrum of hydrogenated silicon carbide nanocrystals (SiC NC) have been determined by first principles calculations. We show that the reconstructed surface can significantly change not just the onset of absorption but the shape of the spectrum at higher energies. We compare our results with two recent experiments on ultrasmall SiC NCs.

Introducing Color Centers to Silicon Carbide Nanocrystals for In Vivo Biomarker Applications: A First Principles Study

2013 ◽  
Vol 740-742 ◽  
pp. 641-644
Author(s):  
Bálint Somogyi ◽  
Viktor Zólyomi ◽  
Adam Gali
Keyword(s):  
Silicon Carbide ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Near Infrared ◽  
Living Cells ◽  
Time Dependent ◽  
Color Centers ◽  
Dependent Density

Molecule-sized fluorescent emitters are much sought-after to probe biomolecules in living cells. We demonstrate here by time-dependent density functional calculations that the experimentally achievable 1-2 nm sized silicon carbide nanocrystals can emit light in the nearinfrared region after introducing appropriate color centers in them. These near-infrared luminescent silicon carbide nanocrystals may act as ideal fluorophores for in vivo bioimaging.

scholarly journals Requirements of first-principles calculations of X-ray absorption spectra of liquid water

2016 ◽  
Vol 18 (1) ◽  
pp. 566-583 ◽  
Author(s):  
Thomas Fransson ◽  
Iurii Zhovtobriukh ◽  
Sonia Coriani ◽  
Kjartan T. Wikfeldt ◽  
Patrick Norman ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Liquid Water ◽  
First Principles ◽  
Density Functional ◽  
Time Dependent ◽  
First Principles Calculations ◽  
Functional Theory ◽  
X Ray ◽  
X Ray Absorption ◽  
Dependent Density

Transition-potential and time-dependent density functional theory XAS calculations are presented for water and ice, showing excellent agreement between TDDFT results and experimental spectra.

scholarly journals Electronic and Optical Properties of Small Hydrogenated Silicon Quantum Dots Using Time-Dependent Density Functional Theory

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Muhammad Mus-’ab Anas ◽  
Geri Gopir
Keyword(s):  
Density Functional Theory ◽  
Quantum Dots ◽  
Absorption Spectrum ◽  
Density Functional ◽  
Time Dependent ◽  
Silicon Quantum Dots ◽  
Functional Theory ◽  
Hydrogenated Silicon ◽  
Small Quantum ◽  
Dependent Density

This paper presents a systematic study of the absorption spectrum of various sizes of small hydrogenated silicon quantum dots of quasi-spherical symmetry using the time-dependent density functional theory (TDDFT). In this study, real-time and real-space implementation of TDDFT involving full propagation of the time-dependent Kohn-Sham equations were used. The experimental results for SiH4and Si5H12showed good agreement with other earlier calculations and experimental data. Then these calculations were extended to study larger hydrogenated silicon quantum dots with diameter up to 1.6 nm. It was found that, for small quantum dots, the absorption spectrum is atomic-like while, for relatively larger (1.6 nm) structure, it shows bulk-like behavior with continuous plateau with noticeable peak. This paper also studied the absorption coefficient of silicon quantum dots as a function of their size. Precisely, the dependence of dot size on the absorption threshold is elucidated. It was found that the silicon quantum dots exhibit direct transition of electron from HOMO to LUMO states; hence this theoretical contribution can be very valuable in discerning the microscopic processes for the future realization of optoelectronic devices.

Photophysical Properties of N-Methyl and N-Acetyl Substituted Alloxazine: A Theoretical Investigation

2021 ◽  
Author(s):  
Huimin Guo ◽  
Xiaolin Ma ◽  
Zhiwen Lei ◽  
Yang Qiu ◽  
Bernhard Dick ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Theoretical Investigation ◽  
Density Functional ◽  
Photophysical Properties ◽  
Time Dependent ◽  
Functional Theory ◽  
Td Dft ◽  
Dependent Density

The electronic structure and photophysical properties of a series of N-Methyl and N-Acetyl substituted alloxazine (AZs) were investigated with extensive density functional theory (DFT) and time-dependent density functional theory (TD-DFT)...

Electronic structure of cubic BaTbO3 from first-principles pseudopotential calculations

2006 ◽  
Vol 84 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G Y Gao ◽  
K L Yao ◽  
Z L Liu
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Pseudopotential Calculations ◽  
Correlation Potential ◽  
Density Contour

First-principles calculations of the electronic structure are performed for cubic BaTbO3 using the plane-wave pseudopotential method within the framework of density functional theory and using the generalized gradient approximation for the exchange-correlation potential. Our calculations show that cubic BaTbO3 is metallic, and that this metallic character is mainly governed by the Tb 4f electrons and the hybridization between the Tb 5d and O 2p states. From the analysis of the density of states, band structure, and charge density contour, we find that the chemical bonding between Tb and O is covalent while that between Ba and TbO3 is ionic. PACS Nos.: 71.15.Mb, 71.20.-b

First-principles study of static displacements in Fe-Pd magnetic shape-memory alloys

2009 ◽  
Vol 1200 ◽  
Author(s):  
Markus E. Gruner
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculations ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Functional Theory ◽  
Lennard Jones ◽  
Theory Comparison

AbstractThis contribution reports static ionic displacements in ferromagnetic disordered Fe70Pd30 alloys obtained by relaxation of the ionic positions of a 108-atom supercell within the framework of density functional theory. Comparison with a simple statistical model based on Lennard-Jones pair interactions reveals that these displacements are significantly larger than can be explained by the different sizes of the elemental constituents. The discrepancies are presumably related to collective displacements of the Fe atoms. Corresponding distortions are experimentally observed for ordered Fe3Pt and predicted by first-principles calculations for all ordered Fe-rich L12 alloys with Ni group elements and originate from details of the electronic structure at the Fermi level.

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