SIZE-DEPENDENCE OF INFRARED SPECTRA IN NIOBIUM CARBIDE NANOCRYSTALS

2012 ◽  
Vol 23 (08) ◽  
pp. 1240001 ◽  
Author(s):  
V. ALVIN SHUBERT ◽  
STEVEN P. LEWIS
Keyword(s):  
Density Functional Theory ◽  
Particle Size ◽  
Density Functional ◽  
Size Dependence ◽  
Niobium Carbide ◽  
Structural Features ◽  
Particle Sizes ◽  
Vibrational Modes ◽  
Functional Theory ◽  
Ir Spectroscopic

Niobium carbide nanocrystals of ~1:1 stoichiometry have recently been observed for particle sizes ranging from Nb4C4 to Nb50C50 . Infrared (IR) spectroscopic measurements show that a new band of IR vibrational modes appears with increasing particle size at Nb9C9 . Using density-functional theory, we show that the vibrational modes in the new band involve structural features present only in nanocrystals with three or more atomic layers in every direction. The Nb9C9 nanocrystal is right at this structural threshold.

Threshold Photoionization and Density Functional Theory Studies of the Niobium Carbide Clusters Nb3Cn(n= 1−4) and Nb4Cn(n= 1−6)

2008 ◽  
Vol 112 (25) ◽  
pp. 5582-5592 ◽  
Author(s):  
Viktoras Dryza ◽  
Matthew A. Addicoat ◽  
Jason R. Gascooke ◽  
Mark. A. Buntine ◽  
Gregory F. Metha
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Niobium Carbide ◽  
Functional Theory

Iron Chelation by thiocytosine: Investigating electronic and structural features for describing tautomerism and metal chelation processes

2021 ◽  
pp. 1-8
Author(s):  
Azadeh Jafari Rad ◽  
Maryam Abbasi ◽  
Bahareh Zohrevand
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Molecular Orbital ◽  
Density Functional ◽  
Biological Systems ◽  
Iron Chelation ◽  
Structural Features ◽  
Metal Chelation ◽  
Functional Theory

This work was performed regarding the importance of iron (Fe) chelation for biological systems. This goal was investigated by assistance of a model of thiocytosine (TC) for participating in Fe-chelation processes. First, formations of tautomeric conformations were investigated to explore existence of possible structures of TC. Next, Fe-chelation processes were examined for all four obtained tautomers of TC. The results indicated that thiol tautomers could be seen at higher stability than thio tautomers, in which one of such thiol tautomers yielded the strongest Fe-chelation process to build FeTC3 model. As a consequence, parallel to the results of original TC tautomers, Fe-chelated models were found to be achievable for meaningful chelation processes or sensing the existence of Fe in media. Examining molecular orbital features could help for sensing purposes. The results of this work were obtained by performing density functional theory (DFT) calculations proposing TC compounds suitable for Fe-chelation purposes.

A Density Functional Theory Study of Coniferyl Alcohol Intermonomeric Cross Linkages in Lignin - Three-Dimensional Structures, Stabilities and the Thermodynamic Control Hypothesis

Holzforschung ◽  
2003 ◽  
Vol 57 (2) ◽  
pp. 150-164 ◽  
Author(s):  
B. Durbeej ◽  
L.A. Eriksson
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Structural Features ◽  
Density Functional Theory Study ◽  
Thermodynamic Control ◽  
Functional Theory ◽  
Quantitative Correlation ◽  
Control Hypothesis

Summary Density functional theory methods are utilized to investigate structural features and stabilities of the most common lignin dimerization products. It is found that intra-molecular hydrogen bonding acts as a stabilizing force in the lowest-energy conformer(s) of several different dimeric lignin structures. Furthermore, the calculations show that the hypothesis of thermodynamic control of monolignol dimerization accounts for some of the results obtained in experimental studies aimed at determining the ratios of intermonomeric linkages. A quantitative correlation between experimentally observed ratios and calculated relative energies cannot, however, be pointed out.

Identifying and explaining vibrational modes of quinacridones via temperature-resolved terahertz spectroscopy: absorption experiments and solid-state density functional theory simulations

2020 ◽  
Vol 22 (35) ◽  
pp. 19672-19679 ◽  
Author(s):  
A. D. Squires ◽  
Adam J. Zaczek ◽  
R. A. Lewis ◽  
Timothy M. Korter
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Density Functional ◽  
Terahertz Spectroscopy ◽  
State Density ◽  
Spectral Features ◽  
Thermal Contraction ◽  
Vibrational Modes ◽  
Functional Theory

New spectral features and anomalous shifting of vibrational modes of beta quinacridone are revealed, unusual thermal contraction the likely origin.

Electronic Structure, Nonlinear Optical Properties, and Vibrational Analysis of Ethyl benzoate by Density Functional Theory

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Tanveer Hasan ◽  
P. K. Singh
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Vibrational Analysis ◽  
Ethyl Benzoate ◽  
Computational Method ◽  
Basis Set ◽  
Vibrational Modes ◽  
Normal Coordinate ◽  
Functional Theory ◽  
Vibrational Bands

This work deals with the vibrational spectroscopy of Ethyl benzoate (C9H10O2). The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) using standard HF/6-31G(d,p) and B3LYP/6-31G(d,p) methods and basis set combinations. The vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes.

Development of nonlinear optical materials promoted by density functional theory simulations

2014 ◽  
Vol 28 (27) ◽  
pp. 1430018 ◽  
Author(s):  
Xingxing Jiang ◽  
Lei Kang ◽  
Siyang Luo ◽  
Pifu Gong ◽  
Ming-Hsien Lee ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Functional Materials ◽  
Dft Method ◽  
Structural Features ◽  
Great Success ◽  
Structure Property ◽  
Functional Theory ◽  
Nlo Property

Nonlinear optical (NLO) crystals are very important optoelectronic functional materials and their developments have significantly contributed to the progress of laser science and technology for decades. In order to explore new NLO crystals with superior performances, it is greatly desirable to understand the intrinsic relationship between the macroscopic optical properties and microscopic structural features in crystals. In this paper, the applications of density functional theory (DFT) method to the elucidation of the structure-property relationship and to the exploration on novel NLO materials in the ultraviolet and infrared spectrum regions are reviewed. The great success in the linear and NLO property predictions has been achieved using the first-principles computational simulations, and the mechanism understanding obtained by various analysis tools can give substantial guidance to the search and design of new NLO crystals.

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