scholarly journals Effet of edge fluorination and chlorination on structures, stability, electronic and charge transport properties of benzo[o]bistriphenyleno[2,1,12,11-efghi:2',1',12',11'-uvabc]ovalene molecule : DFT study.

2021 ◽  
Author(s):  
Marius Ousmanou Bouba ◽  
Fridolin Tchangnwa Nya ◽  
Christine Yvette Ngui ◽  
Jean Marie Ndjaka
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Charge Carriers ◽  
Bandgap Energy ◽  
Electron Affinities ◽  
New Materials ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Theoretical Investigations ◽  
Good Agreement

Abstract We have investigated the structures, electronic properties, hole and electron mobilities of fluorinated and chlorinated nanographene of benzo[o]bistriphenyleno[2,1,12,11-efghi:2',1',12',11'-uvabc]ovalene (TCHG) molecules, us- ing the density functional theory (DFT) and Markus-Hush charge transfer theory. The calculated geometric parameters and the IR spectrum for chlorinated TCHG are in good agreement with the experimental data. Our theoretical investigations have shown that fluorination and chlorination significantly reduce the bandgap energy of TCHG. The obtained adiabatic electron affinities (AEAs) values are 2.76 and 2.93 eV respectively, indicating the air-stable materials. The calculation of charge carriers mobilities in chlorinated dimer shows that the mobility of the electrons is ten times that of the holes, suggesting an n-type behavior. We have shown that the fluorination and chlorination of TCHG are promising pathways for the design of new materials useful in optoelectronics

Anisotropically Nanostructured Silicon: A First-Principle Approach.

2004 ◽  
Vol 832 ◽  
Author(s):  
Yuri Bonder ◽  
Chumin Wang
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
First Principle ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Nanostructured Silicon ◽  
Plane Anisotropy ◽  
The Density Functional Theory ◽  
The Difference ◽  
Good Agreement

ABSTRACTOptical properties of birefringent porous-silicon layers are studied within the density functional theory. Starting from a (110)-oriented supercell of 32 silicon atoms, columns of atoms in directions [100] and [010] are removed and the dangling bonds are saturated with hydrogen atoms. The results show an in-plane anisotropy in the dielectric function and in the refractive index (n). The difference Δn defined as n[110] -n[001] is compared with experimental data and a good agreement is observed. Also, the possibility in determining the morphology of pores by using polarized lights is analyzed.

Theoretical calculations of stability, mechanical and thermodynamic properties of IVA group Willemite-II nitrides

2015 ◽  
Vol 14 (04) ◽  
pp. 1550024 ◽  
Author(s):  
Ying-Chun Ding ◽  
Min Chen ◽  
Wen-Juan Wu
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Mechanical Anisotropy ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Good Agreement

The structural stability and mechanical and thermodynamic properties of WII- A 3 N 4 ( A=C , Si , Ge and Sn ) are calculated by first-principles calculations based on the density functional theory. The calculated lattice parameters and elastic constants of WII- A 3 N 4 ( A=C , Si , Ge and Sn ) are in good agreement with the experimental data and previously calculated values. WII- A 3 N 4 ( A=C , Si , Ge and Sn ) compounds are also found to be thermodynamically and mechanically stable. The results suggest that hardness of WII- C 3 N 4 is the hardest of these C 3 N 4 polymorphs. The hardness of WII- Sn 3 N 4 is the smallest among WII- A 3 N 4 ( A=C , Si , Ge and Sn ). Furthermore, the mechanical anisotropy, Debye temperature, the minimum thermal conductivity and thermodynamic properties of WII- A 3 N 4 ( A=C , Si , Ge and Sn ) compounds can be investigated.

scholarly journals Perhalogenation and Percyanation of Coronene for Characterization of the New Efficient Organic Semiconductors for Charge Transport

2021 ◽  
Author(s):  
Marius Ousmanou Bouba ◽  
Fridolin Tchangnwa Nya ◽  
Alhadji Malloum ◽  
Jeanet Conradie ◽  
Jean Marie Ndjaka
Keyword(s):  
Organic Semiconductors ◽  
Density Functional ◽  
Functional Theory ◽  
Vibrational Assignments ◽  
Ambipolar Behavior ◽  
The Density Functional Theory ◽  
Theoretical Investigations ◽  
Stable Material ◽  
Good Agreement

Abstract We have investigated the structures, electronic properties, hole and electron mobilities of perfluorinated, perchlorinated and percyanated coronene molecules, using the density functional theory (DFT) at the B3LYP-D3/6-311++G(d,p) and ωB97XD/6-311++G(d,p) levels and Markus-Hush charge transfer theory. The calculated geometric parameters for coronene and perchlorocoronene are in good agreement with the experimental data. Our theoretical investigations have shown B3LYP-D3 functional is suitable to well define vibrational assignments for studied molecules. We have shown that the per-halogenation and per-cyanation of coronene increases the adiabatic electron affinities (AEAs) and reduces the LUMO levels and the hole mobilities thus indicating an ambipolar behavior and air-stable material. We have shown that the percyanation of coronene is a promising pathway for the design of new materials useful in optoelectronics.

Investigations of the Optical Properties of LaNi5 and LaNi4.5Sn0.5

2013 ◽  
Vol 321-324 ◽  
pp. 495-498 ◽  
Author(s):  
Dong Chen ◽  
Chao Xu
Keyword(s):  
Experimental Data ◽  
Refractive Index ◽  
Optical Properties ◽  
Density Functional ◽  
Low Frequency ◽  
Potential Method ◽  
Frequency Region ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Pseudo Potential

The reflectivity, loss function, refractive index, extinction coefficient and dielectric function of the LaNi5and LaNi4.5Sn0.5intermetallic compounds are investigated through the plane-wave pseudo-potential method based on the density functional theory. The effects of Sn impurity are discussed and some interesting features are found in the low frequency region. Some important optical properties such as static dielectric constant and static refractive index are obtained. The equation [n (0)]2=ε1(0)is satisfied according to our calculation, which indicates that our results are correct and reasonable. Nevertheless, the calculated results need to be testified in the future due to the lack of experimental data.

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

scholarly journals Solid-State and Theoretical Investigations of Some Banister-Type Macrocycles with 2,2’-Aldoxime-1,1’-Biphenyl Units

2021 ◽  
Vol 9 ◽  
Author(s):  
Ioan Stroia ◽  
Ionuţ -Tudor Moraru ◽  
Maria Miclăuş ◽  
Ion Grosu ◽  
Claudia Lar ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Density Functional ◽  
Alkali Metal Ions ◽  
Functional Theory ◽  
State Data ◽  
Supramolecular Associations ◽  
Theoretical Investigations ◽  
The Stability ◽  
Good Agreement

In the context of helical chirality, bridging of biphenyl units leads to banister-type compounds and the stability of the resulted atropisomers may increase dramatically if suitable changes are performed in the linker unit that coils around the biphenyl moiety. A rigorous density functional theory (DFT) study was conducted for macrocycles containing rigid oxime ether segments connected to the biphenyl backbone in order to determine how the rotation barriers are influenced by the presence of either a flexible oligoethyleneoxide or a more rigid m–xylylene component in the macrocycle. The calculated values for the racemization barrier were in good agreement with those obtained experimentally and confirm the benefit of introducing a more rigid unit in the macrocycle on the stability of atropisomers. Solid-state data were obtained and computed data were used to assess the contribution brought by supramolecular associations observed in the lattice to the stabilization of the crystal structure. Beside introducing rigidity in the linker, complexation of flexible macrocycles with alkali metal ions is also contributing to the stability of atropisomers, leading to values for the racemization barrier matching that of the rigid macrocycle. Using diethylammonium cation as guest for the macrocycle, a spectacular increase in the barrier to rotation was observed for the resulted pseudo[2]rotaxane.

Structural and Magnetic Properties of Mn2NiZ (Z = Ga, In, Sn, Sb) Heusler Alloys from Ab Initio Calculations

2015 ◽  
Vol 233-234 ◽  
pp. 229-232 ◽  
Author(s):  
Vladimir V. Sokolovskiy ◽  
Mikhail A. Zagrebin ◽  
Y.A. Sokolovskaya ◽  
Vasiliy D. Buchelnikov
Keyword(s):  
Magnetic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Heusler Alloys ◽  
Martensitic Transition ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structural And Magnetic Properties ◽  
Structure Calculations ◽  
Good Agreement

The structural and magnetic properties of Mn-based stoichiometric Heusler alloys have investigated by means of ab initio calculations in framework of the density functional theory. First principles electronic structure calculations have shown that Mn2NiZ (Z = Ga, In, Sn, Sb) alloys are ferrimagnets with antiparallel alignment between the Mn atoms. The martensitic transition can be realized in Mn2NiGa and Mn2NiSn alloys with tetragonal ratio of 1.27 and 1.16, respectively. Calculated properties are in a good agreement with available experimental data.

Theoretical Study of the Electronic Structures of Li-Doped ZnO

2012 ◽  
Vol 535-537 ◽  
pp. 214-218
Author(s):  
Qi Xin Wan ◽  
Jia Yi Chen ◽  
Zhi Hua Xiong ◽  
Dong Mei Li ◽  
Bi Lin Shao ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Formation Energy ◽  
Lattice Distortion ◽  
Theoretical Study ◽  
Functional Theory ◽  
Li Doping ◽  
The Density Functional Theory ◽  
Doped Zno ◽  
Good Agreement

The first-principles with pseudopotentials method based on the density functional theory was applied to calculate the geometric structure, the formation energy of impurities and the electronic structure of Li-doped ZnO. In the system of Li-doped ZnO, LiZn can not result in lattice distortion. In contrast with that case, LiO and Lii result in lattice distortion after Li doping in ZnO. In Li-doped ZnO, LiO is the most unstable than the other cases. Simultaneously, Lii is more stable than LiZn according to that Lii has smaller formation energy. Furthermore, the electronic structure of Li-doped ZnO indicates that that LiZn behaves as acceptor, while Lii behaves as donor. In conclusion, in Li-doped ZnO, Lii is always in the system to compensate the acceptor. Singly doping Li in ZnO is difficult to gain p-ZnO for the self-compensation. The results are in good agreement with other calculated and experimental results.

First-Principles Calculations of the Structural, Electronic, Optical and Mechanical Properties of CdS, CdSe and CdTe

2013 ◽  
Vol 665 ◽  
pp. 302-306 ◽  
Author(s):  
Sheetal Sharma ◽  
Ajay Singh Verma
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Zinc Blende ◽  
Optical And Mechanical Properties ◽  
Good Agreement

The structural, electronic, optical and elastic properties of zinc-blende compounds (CdX, X = S, Se and Te), were studied using full-potential augmented plane wave plus local orbitals method (FP-LAPW+ lo) within density functional theory, using generalized gradient approximation (GGA). Geometrical optimization of the unit cell (lattice constant, bulk modulus and its pressure derivative) is in good agreement with experimental data. Results for band structures, density of states, and elastic constants (C11, C12 and C44) are presented. We also report our results on optical properties like the complex dielectric functions and the refractive index (n) of these compounds. Our results are in reasonable agreement with the available theoretical and experimental data.

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