| 1. |
- Nisar, Jawad, 1980-, et al.
(författare)
-
Study of electronic and optical properties of BiTaO4 for photocatalysis
- 2012
-
Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley-VCH Verlagsgesellschaft. - 1610-1634 .- 1610-1642. ; 9:7, s. 1593-1596
-
Tidskriftsartikel (refereegranskat)abstract
- We present the optical absorption spectrum of BiTaO4 using the photo acoustic spectroscopy (PAS) technique and first principle approach. Band gap have been estimated 2.65 and 2.45 eV using PAS method and DFT calculations, respectively. Position of reduction and oxidation level with respect to vacuum level are identified, which shows that BiTaO4 can be used as photocatalyst for hydrogen production. Electronic structure is explained by plotting total density of states (TDOS).
|
|
| 2. |
- Almeida, Roseley, et al.
(författare)
-
Theoretical Evidence behind Bifunctional Catalytic Activity in Pristine and Functionalized Al2C Monolayers
- 2018
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 19:1, s. 148-152
-
Tidskriftsartikel (refereegranskat)abstract
- First principles electronic structure calculations based on the density functional theory (DFT) framework are performed to investigate hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on two-dimensional Al2C monolayers. In addition to the pristine Al2C monolayer, monolayers doped with Nitrogen (N), Phosphorous (P), Boron (B), and Sulphur (S) are also investigated. After determining the individual adsorption energy of hydrogen and oxygen on the different functionalized Al2C monolayers, the adsorption free energies are predicted for each of the functionalized monolayers in order to assess their suitability for HER or OER. The density of states and optical absorption spectra calculations along with the work function of the functionalized Al2C monolayers enable us to gain a profound understanding of the electronic structure for the individual system and their relation to the water splitting mechanism.
|
|
| 3. |
- Souza de Almeida, Jailton, 1971-
(författare)
-
Designing and Tuning the Properties of Materials by Quantum Mechanical Calculations
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In many materials, changes in chemical composition, pressure or temperature can induce metal to insulator transitions. It is recently observed in yttrium hydride, for example, changes from a shiny mirror (YH2) to a transparent window (YH3), which has important technological application in optical devices. We have tuned the above transition by choosing pressure instead of composition. Our predicted finding is confirmed by recent experiments and opens a new way to design optical switches.The unique role that gold plays in society is to a large extent related to the fact that it is the most noble of all metals.We have studied the noble nature of gold by choosing pressure as tool. Our prediction shows that gold transforms from a face centered cubic to an hexagonal closed packed phase above 200 GPa whereas platinum, another noble metal, does not show any phase transition up to 500 GPa. This prediction has also been confirmed by experiments suggesting that platinum is more noble than gold.The growing concern about climate change and fossil fuel availability, the direct conversion of solar irradiation into electricity appears to be an ideal alternative to conventional energy sources. Power generation by solar cells is a direct method of solar energy conversion. We report a new cubic phase of TiO2 which can be stabilized at ambient conditions. This phase has an absorption three or four orders of magnitude larger than the conventional state-of-the-art solar cell based on anatase TiO2. Therefore, we are introducing a well established material with a new structure for future generation solar cells. The same effect is also observed in cubic SnO2.Electronic and optical properties of other materials such as BexZn1-xTe, RuO2 and IrO2 are also studied in present thesis. In particular, for BexZn1-xTe, we have used composition as a tool to tune the optical properties.
|
|
| 4. |
|
|
| 5. |
- Souza de Almeida, Jailton, et al.
(författare)
-
Tuning the structural, electronic, and optical properties of BexZn1-xTe alloys
- 2006
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:6, s. 061913-
-
Tidskriftsartikel (refereegranskat)abstract
- A series of first principles calculations have been carried out to investigate structural, electronic, and optical properties of BexZn1-xTe alloys for five beryllium compositions. Our results show that the lattice constant scales linearly with beryllium composition and there is a direct-to-indirect band gap crossover nearly at the composition of 20%. It is also found that no bowing effect in the absorption edge is observed unlike other II-VI semiconductor alloys. Our results are in good qualitative agreements with experimental observations.
|
|
