Home About us Contact
|
Home About us Contact | ||
|
|
||
Level Calculations (level + calculation)
Selected AbstractsThe growth of In-rich InGaN/GaN single quantum wells by metalorganic chemical vapor depositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Hyun Jin Kim Abstract In-rich InGaN/GaN single quantum wells were grown by metalorganic chemical vapor deposition for the first time to the best of our knowledge. The structures consist of a 2-,m thick GaN buffer layer, a 2-nm thick In-rich InGaN single quantum well, and a 20 nm thick GaN capping layer. Single quantum well structures were examined by transmission electron microscopy. Photoluminescence emissions from the single quantum well samples were observed at wavelengths ranged from 400 nm to 500 nm depending upon the growth conditions of the InN layer. From a simple energy level calculation, we found the possibility of extremely large emission peak shift with well thickness. [source] Vertical excitation energies for ribose and deoxyribose nucleosidesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2007Remmick So Abstract Vertical excitation energies for DNA and RNA nucleosides are determined with electron structure calculations using the time-dependent density functional theory (TDDFT) method at the B3LYP/6-311++G(d,p) level for nucleoside structures optimized at the same level of theory. The excitation energies and state assignments are verified using B3LYP/aug-cc-pVDZ level calculations. The nature of the first four excited states of the nucleosides are studied and compared with those of isolated bases. The lowest n,* and ,,* transitions in the nucleoside remain localized on the aromatic rings of the base moiety. New low-energy n,* and ,,* transitions are introduced in the nucleosides as a result of bonding to the ribose and deoxyribose molecules. The effect on the low-lying excited state transitions of the binding to phosphate groups at the 5,- and 3,,5,-hydroxyl sites of the uracil ribose nucleoside are also studied. Some implications of these calculations on the de-excitation dynamics of nucleic acids are discussed. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007. [source] Complete basis set prediction of methanol isotropic nuclear magnetic shieldings and indirect nuclear spin,spin coupling constants (SSCC) using polarization-consistent and XZP basis sets and B3LYP and BHandH density functionalsMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2009Teobald Kupka Abstract Efficient B3LYP and BHandH density functionals were used to estimate methanol's nuclear magnetic isotropic shieldings and spin,spin coupling constants in the basis set limit. Polarization-consistent pcS- n and pcJ- n (n = 0, 1, 2, 3 and 4), and segmented contracted XZP, where X = D, T, Q and 5, basis sets were used and the results fitted with simple mathematical formulas. The performance of the methods was assessed from comparison with experiment and higher level calculations. 1J(CH) and 3J(HH) values were determined from very diluted solutions in deuterochloroform and compared with theoretical predictions. The agreement between complete basis set (CBS) density functional theory (DFT) predicted isotropic shieldings and spin,spin values and experiment was good. The BHandH/pcS- n methanol shieldings obtained using structures optimized at the same level of theory are approaching the accuracy of the advanced coupled-cluster-singles-doubles-approximate triples (CCSD(T)) calculations. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hypothetically superhard boron carbide structures with a B11C icosahedron and three-atom chainPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2009Sezgin Aydin Abstract The structural and mechanical properties are investigated for the phases of superhard boron carbide, B4C, by performing DFT/PW91 level calculations. In addition to B12 icosahedra and CCC chains, we suggest new types of hypothetically stable rhombohedral structures of boron carbide, configurations that consist of one icosahedron, B11C, and a three-atom chain such as CBC, CCB and BCC. Our results indicate that all phases are promising superhard materials, the hardness of all of them being greater than 40 GPa. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||