Results 221 to 230 of about 225,991 (262)

Theoretical studies of fluorocarbons part III. Primary, secondary, tertiary and quaternary centres

Journal of Fluorine Chemistry, 1990
Abstract Quantum chemical calculations are used to examine the differences between fully fluorinated alkanes with primary, secondary, tertiary and quaternary centres. Systems studied include C(CF 3 ) n F 4-n (n=0−4), CF 3 [C(CF 3 ) 2 ] p CF 3 (p=1−5), (CF 3 ) 2 CF[C(CF 3 ) 2 ] q CF(CF 3 ) 2 (q=0−3) and CF 3 CF 2 [C(CF 3 ) 2 ] r CF 2 CF 3 (r=0−3).
David L. Cooper, Neil L. Allan, Richard L. Powell   +2 more
openaire   +1 more source

Theoretical Studies of EPR Parameters and Microstructure of the Rhombic Co2+-VAg Centre in AgCl

physica status solidi (b), 2000
The perturbation formulae of EPR g-factors g(i) (i = x, y, z) and hyperfine constants Ai for a 3d(7) (Co2+) ion at a rhombic octahedral site in a crystal are established from a cluster approach. In these formulae, the contributions from the covalency effect, the configuration interaction and the rhombic crystal field are considered and the parameters ...
Wen-Chen Zheng, Shao-Yi Wu
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Theoretical Studies on the M′‐Centre in Alkali Halide Crystals

physica status solidi (b), 1969
AbstractThe results of the theoretical study of the electronic states of the M′‐centre in alkali halides are reported. No empirical parameters are used in this calculation. – The electronic core polarization is taken into account (within the limits of model of the polarizable point ion lattice), and is found to be essential for the charged M′‐centre ...
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Theoretical studies of the dependence of EPR parameters on local structure for the tetragonal Er3+ centres in YVO4 and ScVO4

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
The dependences of the EPR parameters on the local distortion parameters Δθ and ΔR as well as the crystal-field parameters have been studied by diagonalizing the 364×364 complete energy matrices for a tetragonal Er(3+) centre in the YVO4 and ScVO4 crystals. The results show that the local distortion angle Δθ and the fourth-order crystal-field parameter
Rui-Peng, Chai, Dan-Hui, Hao, Xiao-Yu, Kuang, Liang, Liang   +3 more
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Theoretical Study of a Centre-fed Dipole Antenna with Displaced Feed Points in Plasma Medium

IETE Journal of Research, 1970
Theoretical study of the centre-fed dipole antenna with displaced feed points in plasma medium is presented. The cases of the centre-fed dipole antenna with (i) feed points displaced transverse to dipole axis, (ii) feed points displaced along the dipole axis, (iii) feed points displaced arbitrarily, are discussed in detail. Mathematical expressions for
S. P. Kosta, Murli Dhar Singh, N. K. Agarwal, R. P. Agarwal, Upendra Tiwari   +4 more
openaire   +1 more source

Effect of metal centres and substituents on the structure and optoelectronic properties of diarylethene compounds: A theoretical study

Science China Chemistry, 2012
Diarylethene derivatives are a class of fascinating photochromic materials because of their open and closed isomers with different absorption spectra and many other characteristics. To reveal the detailed structure and optoelectronic properties as well as the effect of metal centres and substituents on them, a systematic study on a series of ...
ShuJuan Liu, ChengJiang Yang, WenJuan Xu, YanQin Huang, ShangHui Ye, Qiang Zhao, XiangMei Liu, Wei Huang   +7 more
openaire   +1 more source

Study of the propagation centre in the anionic polymerization of lactams, 1. Spectroscopic and theoretical study of the activated monomer in dimethyl sulfoxide

Macromolecular Chemistry and Physics, 1996
AbstractSolutions of Li, Na and K salts of 3,3‐dimethyl‐2‐piperidone and ε‐caprolactam in dimethyl sulfoxide‐d6 were studied by 6Li, 7Li, 23Na, 1H and 13C NMR, Raman spectroscopy and MNDO molecular orbital calculations. Using NMR relaxation, the dynamics and equilibrium states of solvation, dissociation and cation exchange were clarified.
Jaroslav Kříž, Jaroslav Stehlíček, Jiří Dybal, Jan Hauer, Pavel Schmidt   +4 more
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Theoretical study of the electron paramagnetic resonance parameters and local structure for the tetragonal Ir2+ centre in NaCl

Pramana, 2010
The electron paramagnetic resonance (EPR) parameters (the g factors, hyperfine structure constants and the superhyperfine parameters) for the tetragonal Ir2+ centre in NaCl are theoretically investigated from the perturbation formulas of these parameters for a 5d7 ion in tetragonally elongated octahedra.
Y. -X. Hu, S. -Y. Wu, X. -F. Wang, P. Xu
openaire   +1 more source

Study of accessibility costs and satisfaction comparing a MAS unit incorporated in a Hospital versus a theoretical model in a peripheral centre

Cirugía Española (English Edition), 2011
Geographical barriers are a determining factor in the accessibility of Hospital health care, and structural changes to improve geographic accessibility must be introduced. The purpose of this study is to compare accessibility costs and the level of satisfaction obtained in an adapted Specialist Centre with a peripheral MAS (Major Ambulatory Surgery ...
Ricardo de Miguel, Ibáñez, Juan Carlos Palomo, Sánchez, Saif Adeen Nahban, Al Saied, Javier Alonso, Vallejo, José Manuel Rodríguez, Canales, Carlos Blanco, Priet, Francisco Escribano, Sotos   +6 more
openaire   +2 more sources

Theoretical simulation of V_K-centre migration in KCl. I. A quantum-chemical study

Journal of Physics: Condensed Matter, 1992
Using embedded quantum cluster models, the authors have studied the mechanism of VK-centre 60 degrees reorientation in KCl and LiCl, and have considered the possibility that both one-centre 'dielectric' polarons and 'molecular' polarons (VK centres) coexist in KCl.
A L Shluger, L N Kantorovich, E N Heifets, E K Shidlovskaya, R W Grimes   +4 more
openaire   +1 more source