Optical Properties and Electronic Structures of a Liquid Crystal TBO10A

2011 ◽  
Vol 181-182 ◽  
pp. 110-114
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Liquid Crystal ◽  
Electronic Structures ◽  
Room Temperature ◽  
Tight Binding ◽  
Electronic Structure Calculations ◽  
Scanning Calorimetry ◽  
Absorption Bands ◽  
Rigid Core ◽  
Tight Binding Method ◽  
Structure Calculations

A liquid crystal (LC) N,N-(terephthalylidene) bis (4-octyloxyaniline) (TBO10A) was synthesized at room temperature. The LC TBO10A were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), ultraviolet-visible spectrophotometry, photoluminecence (PL) spectroscopy and electronic structure calculations. In tetrahydrofuran solutions, two optical absorption bands were recorded for TBO10A at about 298 and 379 nm, respectively. Under the 325 nm excitation, dilute tetrahydrofuran solutions of the TBO10A can give off weak blue PL. With Hückel tight-binding method, the electronic structures of the TBO10A were calculated. Our results demonstrated that two absorptions can be attributed to theπ→π* andn→π* transitions in the rigid core of the TBO10A while the PL observed at about 481 nm (2.58 eV) can be assigned to theπ* →ntransition.

Deep-Blue Photoluminescent Properties of a Liquid Crystal TB10A

2011 ◽  
Vol 181-182 ◽  
pp. 33-38 ◽  
Author(s):  
Qing Lan Ma ◽  
Rui Xiong ◽  
Yuan Ming Huang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Electronic Structures ◽  
Room Temperature ◽  
Tight Binding ◽  
Electronic Structure Calculations ◽  
Scanning Calorimetry ◽  
Deep Blue ◽  
Tight Binding Method ◽  
Structure Calculations

A typical liquid crystal (LC) N,N-(terephthalylidene) bis (4-decylbenzenamine) (TB10A) was firstly synthesized at room temperature. The synthesized LC TB10A were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), ultraviolet-visible (UV-vis) spectrophotometry, photoluminecence (PL) spectroscopy and electronic structure calculations. Upon the 325 nm excitation, the dilute tetrahydrofuran solutions of TB10A could give off blue PL. With Hückel tight-binding method, the electronic structures of the TB10A were calculated. Our results demonstrated that the deep-blue PL observed at about 489 nm (2.54 eV) can be assigned to theπ* →ntransition for the TB10A.

ELECTRONIC STRUCTURE CALCULATIONS ON MoTe2 WITH ROTATED PLANES

2005 ◽  
Vol 19 (26) ◽  
pp. 3933-3943
Author(s):  
A. TLAHUICE ◽  
E. FLORES ◽  
D. H. GALVÁN
Keyword(s):  
Electronic Structure ◽  
Diffraction Pattern ◽  
Tight Binding ◽  
Electronic Structure Calculations ◽  
Experimental Measurements ◽  
Metallic Behavior ◽  
Tight Binding Method ◽  
Total Energies ◽  
Structure Calculations ◽  
Good Agreement

Electronic structure calculations have been carried out using Extended Hückel tight-binding method for 2 H — MoTe 2 for the cases both unrotated and with rotated planes. It has been found that relative rotations of the tellurium layers ranging from 5 to 16 degrees have the same total energies and total energies/atom as the unrotated structure. Moreover, an increased in metallic behavior has been observed, as long as the degrees of rotated planes are increased. Finally, good agreement has been found among previous experimental measurements in the diffraction pattern of irradiated MoTe 2 and our calculated 5, 6 and 7 degrees of rotations.

ZERO AND FINITE TEMPERATURE STUDY OF SINGLE FULLERENE CAGES AND CARBON “ONIONS” — GEOMETRY AND SHAPE

1993 ◽  
Vol 07 (29n30) ◽  
pp. 1883-1895 ◽  
Author(s):  
A. MAITI ◽  
C.J. BRABEC ◽  
J. BERNHOLC
Keyword(s):  
Interatomic Potential ◽  
Critical Size ◽  
Tight Binding ◽  
Configurational Entropy ◽  
Electronic Structure Calculations ◽  
Carbon Onions ◽  
Three Body ◽  
Structure Calculations ◽  
Scaling Arguments

Scaling arguments are used to show that above a critical size of several thousand atoms, there is a stability crossover from single to multilayer cages. Conjugate gradient minimization using a classical three-body interatomic potential, as well as tight-binding electronic structure calculations yield ground-state configurations for large fullerene shells that are polyhedral with clearly faceted geometry. The structure, energetics and configurational entropy associated with low-energy defects are calculated and the number of defects estimated as a function of temperature. The role of these thermally generated defects on the shape of large fullerenes is investigated in order to explain the nearly spherical shapes of the newly discovered carbon “onions”.

Stability and Structures of Constitutional Defects in Nonstoichiometric Intermetallic Compounds by First-Principles Calculations

2005 ◽  
Vol 475-479 ◽  
pp. 3111-3114
Author(s):  
Masataka Mizuno ◽  
Hideki Araki ◽  
Yasuharu Shirai
Keyword(s):  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Stoichiometric Composition ◽  
Electronic Structure Calculations ◽  
First Principles Calculations ◽  
Compositional Dependence ◽  
Wide Range ◽  
Formation Energies ◽  
Structure Calculations

Some of intermetallic compounds exist in a wide range of concentration around the stoichiometric composition. First-principles electronic structure calculations have been performed for constitutional defects in non-stoichiometric CoAl and CoTi in order to investigate their stabilities and structural relaxations induced by constitutional defects. For the evaluation of stabilities of constitutional defects, the compositional dependence curves both of formation energies and of lattice parameters are obtained by the calculations employing supercells in various sizes. The lattice relaxations around constitutional defects are discussed by analyzing the change in electronic structures induced by constitutional defects.

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