scholarly journals Terahertz Time Domain, Raman and Fourier Transform Infrared Spectroscopy of Acrylamide, and the Application of Density Functional Theory

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Ramzan Ullah ◽  
Salah Ud-Din Khan ◽  
Muhammad Aamir ◽  
Rasheed Ullah
Keyword(s):  
Density Functional Theory ◽  
Refractive Index ◽  
Time Domain ◽  
Density Functional ◽  
Frequency Range ◽  
Functional Theory ◽  
Average Value ◽  
Experimental Values ◽  
Good Agreement ◽  
Constant Refractive Index

We present terahertz time domain spectra of acrylamide in the frequency range from 0.2 to 2 THz with nearly constant refractive index having an average value of 1.33 and an absorption coefficient. Raman (95–3000 cm−1) and FTIR (450–4000 cm−1) spectra also show good agreement with density functional theory (DFT) B3LYP 6-311G++ (3df 3pd) calculations except C-H and N-H stretching frequencies even after scaling with scale factor of 0.9679. We use MOLVIB to rescale such frequencies to match experimental values.

scholarly journals A computational study of the fluctional behaviour of group 14 substituted ortho-semiquinone radicals

2011 ◽  
Vol 89 (2) ◽  
pp. 235-240 ◽  
Author(s):  
K. U. Ingold ◽  
Gino A. DiLabio
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Rate Constant ◽  
Density Functional ◽  
Computational Study ◽  
Group 14 ◽  
Functional Theory ◽  
Semiquinone Radicals ◽  
Experimental Values ◽  
Good Agreement

The dynamics of the 1,4-migration of some O-substituted 3,5-di-tert-butyl-ortho-semiquinone radicals have been calculated by density-functional theory (DFT). There is very good agreement in the rate constant and Arrhenius parameters between these calculations and experimental values for migration of H, D, and the Me3Si group. For the Me3Sn group, the calculations indicate an incredibly fast migration (k293K = 2.0 × 1012 s–1), a result that is consistent with experimental data (k293K > 109 s–1). Other O-substituents examined by DFT and compared with experimental data were H3C and Me2ClSn.

Density functional theory (DFT) and Hartree–Fock (HF) calculations of potential p–vinylbenzyl chloride-based macroinitiator for atom transfer radical polymerization

2016 ◽  
Vol 94 (3) ◽  
pp. 290-304 ◽  
Author(s):  
Feride Akman
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Potential Energy ◽  
Density Functional ◽  
Energy Surface ◽  
Functional Theory ◽  
Hartree Fock ◽  
Experimental Values ◽  
Good Agreement ◽  
Hf Calculations

The spectroscopic properties of poly (styrene–co–p–vinylbenzyl chloride) (poly (St-co-VBC)) were investigated by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopic techniques. The molecular geometry and vibrational frequencies of macroinitiator, poly (St-co-VBC), were calculated by using density functional theory (DFT) and Hartree–Fock (HF) methods with 6–31 G+ (d, p) as a basis set. Calculated theoretical values are shown to be in good agreement with that of experimental values. An excellent harmony between the two data sets was verified. Besides, the experimental data of macroinitiator were compared with experimental data of its corresponding monomers such as St and VBC. The dimer and trimer forms of macroinitiator are used as significant contributions for getting an accurate interpretation of the experimental frequencies of poly (St-co-VBC). The results revealed that the change from St and VBC to poly (St-co-VBC) should be characterized by the disappearance of the CH2=CH bonds of the vinyl group and the appearance of the aliphatic C–H and CH2 bonds. The geometrical parameters, Mulliken atomic charges and frontier molecular orbitals energies were also calculated using the same theoretical methods. The chemical shifts were calculated by using the gauge–including atomic orbital method and all the theoretically predicted values were shown to be in good agreement with experimental values. Molecular orbital properties, molecular electrostatic potential, and the potential energy surface for the atom transfer radical polymerization (ATRP) of the macroinitiator were studied with DFT and HF calculations. The potential energy surface of the ATRP initiator is decided by their electronic effect and steric hindrance effect simultaneously.

scholarly journals Relationship between crystal structure and thermo-mechanical properties of kaolinite clay: beyond standard density functional theory

2015 ◽  
Vol 44 (28) ◽  
pp. 12550-12560 ◽  
Author(s):  
Philippe F. Weck ◽  
Eunja Kim ◽  
Carlos F. Jové-Colón
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Density Functional Theory ◽  
Density Functional ◽  
Dispersion Interactions ◽  
Kaolinite Clay ◽  
Functional Theory ◽  
Experimental Values ◽  
Good Agreement ◽  
Standard Density

The structural, mechanical and thermodynamic properties of 1 : 1 layered dioctahedral kaolinite clay, Al2Si2O5(OH)4, were investigated using density functional theory corrected for dispersion interactions. Good agreement is obtained with the recent experimental values reported for well-crystallized samples.

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

First-principle investigations on structural, elastic, electronic and thermodynamic properties of ScX3(X = Ir,Pd,Pt and Rh) under high pressure

2015 ◽  
Vol 29 (32) ◽  
pp. 1550201 ◽  
Author(s):  
Bao Chen ◽  
Santao Qi ◽  
Hongquan Song ◽  
Chuanhui Zhang ◽  
Jiang Shen
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
Density Functional ◽  
External Pressure ◽  
First Principle ◽  
Zero Temperature ◽  
Functional Theory ◽  
Change Trend ◽  
Experimental Values

In this paper, the structural, elastic, electronic and thermodynamic properties of [Formula: see text] and [Formula: see text] intermetallic compound are investigated using pseudopotential method based on density functional theory (DFT) under pressure. In this work, the calculated lattice constant and bulk modulus are in accordance with experimental values at zero temperature and zero pressure. The bulk modulus [Formula: see text], shear modulus [Formula: see text] and Young’s modulus [Formula: see text] for [Formula: see text] and [Formula: see text] increase with the increasing external pressure. It is noted that [Formula: see text] of investigated compound has the largest [Formula: see text], [Formula: see text] and [Formula: see text]. The results of [Formula: see text] and [Formula: see text] have the same change trend, but [Formula: see text] presents an irregular change for [Formula: see text] and [Formula: see text]. The density of states for [Formula: see text] and [Formula: see text] are investigated at 0, 30 and 50 GPa. In addition, the thermodynamic properties as a function of temperature at different pressure are also studied.

scholarly journals STRUCTURAL AND ELECTRONIC PROPERTIES OF BRIDGED BITHIOPHENE S-OXIDES (BTO) WITH S, S=O, O, SiH2 and BH2 BRIDGE: SEMI-EMPIRICAL AND AB INITIO STUDY

2010 ◽  
Vol 18 (18) ◽  
pp. 1-10
Author(s):  
Banjo Semire ◽  
Isaiah Ajibade Adejoro ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Empirical Methods ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Semi Empirical ◽  
Good Agreement

In this paper, we theoretically studied the geometries, stabilities, electronic and thermodynamic properties of bridged bithiophene S-oxide (BTO-X) derivates (with X = BH2, SiH2, S, S=O, and O) by using semi-empirical methods, ab-initio, and Density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with that of B3LYP/6-31G(d). The bandgap calculated by B3LYP/6-31G(d) ranged from 3.94eV (BTO-O)-3.16eV (BTO-BH2). The absorption λmax calculated suing B3LYP/6-31G(d) shifted to longer wavelength with X=BH2, SiH2, and S=O due to enhancement of π-conjugated system whereas, BTO-S and BTO-O shifted to shorter wavelengths as compared to dimmer thiophene S-oxide (2TO).

An O(N) Time-Domain Method for Time-Dependent Density Functional Theory

2009 ◽  
Author(s):  
Chi Yung Yam ◽  
Fan Wang ◽  
GuanHua Chen ◽  
George Maroulis ◽  
Theodore E. Simos
Keyword(s):  
Density Functional Theory ◽  
Time Domain ◽  
Density Functional ◽  
Time Domain Method ◽  
Time Dependent ◽  
Functional Theory ◽  
Domain Method ◽  
Dependent Density

Electric Field Gradient in Aluminium due to Vacancy and Muon

1992 ◽  
Vol 47 (1-2) ◽  
pp. 45-48
Author(s):  
M. J. Ponnambalam
Keyword(s):  
Density Functional Theory ◽  
Electric Field ◽  
Density Functional ◽  
Near Neighbour ◽  
Electric Field Gradients ◽  
Functional Theory ◽  
Field Gradients ◽  
Analytic Expression ◽  
Valence Effect ◽  
Good Agreement

AbstractThe electric field gradients (EFG) in aluminium due to a monovacancy and the interstitial muon are evaluated. The valence effect EFG qv is calculated using perturbed electron density δn(r)values obtained from density functional theory in an analytic expression which is valid at all distances from the impurity. The size effect EFG qs is evaluated using a new oscillatory form for the near neighbour (nn) displacements. The numerical values of qs are computed using fractional nn displacements available in the literature. For the total EFG good agreement with experiment is obtained without the use of any parameter.

scholarly journals Structure and Symmetrization of Hydrogen Bonding in Ices VIII and X at High Pressure: A Density Functional Theory Approach

2015 ◽  
Vol 19 (2) ◽  
pp. 14-18
Author(s):  
Nurapati Pantha ◽  
Narayan Prasad Adhikari
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Science And Technology ◽  
Group Symmetry ◽  
Initial Structure ◽  
Theory Approach ◽  
Functional Theory ◽  
Cell Parameters ◽  
Transition Pressure ◽  
Experimental Values

We study the change in structural properties of ice by taking initial structure of “ice VIII”, with space group symmetry I41/amd, as a function of elevating pressure up to 120 GPa in density-functional theory (DFT) level of calculations implemented by Quantum ESPRESSO package. Consistent with the standard laws of thermodynamics, our calculations show that the physical size (volume and cell parameters) of the unit cell compresses monotonically on increasing pressure. We also compare our DFT results of these parameters with the available experimental values performed at finite temperature. The comparison shows good agreement between the quantities, within 5%, with slightly higher experimental values. At 100 GPa of pressure, hydrogen atom comes exactly at the midpoint of two boneded oxygens, called hydrogen-bonded symmetrization, which at low pressure remains nearby one of the oxygens. This symmmetrized structure is characterized by a new phase of the system known as “ice X” and the boundary pressure, 100 GPa, defines the transition pressure (P0) for changing phase from “ice VIII” to “ice X”. The transition pressure (P0) of the present work agrees well within 2% of previously reported results.Journal of Institute of Science and Technology, 2014, 19(2): 14-19Journal of Institute of Science and Technology, 2014, 19(2): 14-18

scholarly journals Analysis of vibratinal spectra of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,7-dinitro derivatives based on density functional theory calculations

2007 ◽  
Vol 5 (1) ◽  
pp. 201-220 ◽  
Author(s):  
Khaled Bahgat ◽  
Abdel Ragheb
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Basis Set ◽  
Normal Coordinate ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Vibrational Bands ◽  
Good Agreement

AbstractThe geometry, frequency and intensity of the vibrational bands of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,7-dinitro derivatives were obtained by the density functional theory (DFT) calculations with Becke3-Lee-Parr (B3LYP) functional and 6-31G* basis set. The effects of chloride, bromide, iodide and nitro substituent on the vibrational frequencies of 8-hydroxyquinoline have been investigated. The assignments have been proposed with aid of the results of normal coordinate analysis. The observed and calculated spectra are found to be in good agreement.

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