Author: George Maroulis

We report a study of the performance of density functional theory (DFT) methods in the prediction of electric properties for the ozone molecule. We have used a large, flexible basis set for the calculation of the dipole moment and the dipole (hyper)polarizability with the B1LYP, B3LYP, B3P86, B3PW91, G96PW91 and MPW91PW91 methods. The results are compared to high-level, conventional ab initiomethods. We rely on a rigorous approach in order to evaluate the proximity and similarity of theoretical descriptions obtained via DFT and conventional ab initiomethods. We find that compared to the most accurate ab initio, DFT methods predict reliable dipole polarizabilities and second dipole hyperpolarizabilities for ozone. Agreement is less good for the dipole moment and the first dipole hyperpolarizability. Overall, the performance of the DFT is similar to that of the accurate ab initiomethods.

In: Computing Letters

Study of interaction of NO and (NO)2 molecules with silver clusters has been carried out using the hybrid method S2LYP based on density functional theory (DFT). The role of cluster charge and site of adsorption on N–O stretch frequency, adsorption energy and geometry has been investigated. Four cluster models of different size have been used for simulation of (NO)2 adsorption on Ag{111} surface. The pronounced effect of N–N bond shortening in comparison with gaseous (NO)2 has been found due to adsorption of (NO)2 on silver cluster. This phenomenon is important as possible pathway of N–N bond formation in catalytic fragmentation of NO molecule. The calculations showed that the silver octamer is the best candidate for simulation of formation and fragmentation of (NO)2 on Ag{111} surface within the cluster model.

In: Computing Letters

We present a rigorous analysis of the performance of a set of twelve DFT methods on the calculation of the static electric polarizability and hyperpolarizability of the lithium tetramer. Our analysis reveals essential similarities and dissimilarities in the performance of these methods.

In: Computing Letters
Authors: Ayan Datta and Swapan K Pati

We compare and contrast the structure and bonding aspects in clusters of alkali and alkaline earth metals: Li and Be respectively. The binding energies for both the clusters increase with increase in cluster size, however, for Be, the binding energies increase much rapidly due to stronger cooperative phenomenon. For the high spin Li clusters, the binding energies are moderate and show a remarkable odd-even effect. Similar oscillations are also observed in their π-electron binding energies. The origin of such effects is traced to the ferromagnetic interactions arising from the unpaired electrons for the high spin clusters. On the contrary, for Be, no such odd-even effects are observed due to absence of unpaired electrons.

In: Computing Letters

We have calculated the bond-length dependence of the static dipole polarizability and hyperpolarizability of F2 relying on finite-field density functional calculations. At the internuclear separation of Re = 2.66816 a0 we obtain α/ e2a0 2Eh -1 = 8.73 (B3LYP) and 8.60 (B3PW91),α./ e2a0 2Eh -1 = 6.42 (B3LYP) and 6.32 (B3PW91), γ / e4a0 4Eh -3 = 535 (B3LYP) and 503 (B3PW91) with a large, flexible [9s6p4d1f] basis set. For all three properties we observe that both B3LYPand B3PW91 yield values above the more accurate CCSD(T) results: CCSD(T) < B3PW91 < B3LYP. The discrepancy between DFT and conventional ab initio methods is more pronounced for the anisotropy of the (hyper)polarizability.

In: Computing Letters

Supramolecular chemistry now has become a central part of the research activities. Basically, it mostly concerns molecular recognition and self aggregation by non-covalent weak intermolecular interactions, such as hydrogen bonding, .π-π. stacking, and van der Waals interactions. The computational applications on such large systems are limited for their structural complexity. Several examples of the computational approaches to understand molecular recognition and self-aggregation are discussed. Firstly, bifunctional (fluorescence and visible light absorption) anion sensing mechanism is supported by the DFT calculations. Secondly, an experimentally observed selective recognition of Cu2+ by an azobenzeneappended receptor, which can exhibit Cu2+ selectivity by color change, is discussed based on computational approach. Finally, the intermolecular interaction, which is useful for predicting the self-assembled structures, can be understood by replicating the monomer unit and manipulating the translation and rotation.

In: Computing Letters

series of push-pull chromophores built around thiophene-based . π-conjugating spacers and bearing various types of amino-donors and cyanovinyl-acceptors have been analyzed by means of UV-Vis- NIR spectroscopic measurements. Density functional theory (DFT) calculations have also been performed to help the assignment of the most relevant electronic features and to derive useful information about the molecular structure of these NLO-phores. The effects of the donor/acceptor substitution in the electronic and molecular properties of the .π -conjugated spacer have been addressed. The effectiveness of the intramolecular charge transfer (ICT) has also been tested as a function of the nature of the end groups (i.e., electron-donating or electron-withdrawing capabilities).

In: Computing Letters

The lowest energy states of NFe4N, NFe4O, F e4N2, Fe4NO, and CFe4O, along with their singly negatively and positively charged ions, are optimized using density functional theory with generalized gradient approximation for the exchange-correlation functional (DFT-GGA). It is found that NO attaches dissociatively, independent of the charge on the Fe4 cluster, while N2 attaches dissociatively to Fe4 and Fe4 , but associatively to Fe4 +. CO attaches associatively independent of the cluster charge. The results of these computations, along with the results of previous calculations, are used for evaluating the energetics of Fe4A+B→Fe4C +D, where A, B, C, and D are C, O, N, their dimers, or NCO. A strong dependence on the order of attachment of reagents to the Fe4 cluster is observed. For example, the Fe4CO+O2→Fe4O+CO2 is highly exothermic (-4.48 eV), while the complimentary reaction Fe4O2+ CO → Fe4O+CO2 is endothermic (+0.43 eV).

In: Computing Letters

; these will be put in quota- tion marks and are not included in the following list. K.-D. Klass et al. / Insect Systematics & Evolution 40 (2009) 361–387 367 att anterior tendon of tarsus dei dorsal extension of sclerite itts dft dorsal fold on distal margin of tibia epl euplantula of tarsomere (most

In: Insect Systematics & Evolution

chiffrements correspondants. Ce lettré aurait dft normalement-il est mort au débutde Igso - avoir son nom mentionn6 sur la couverture de celui des 6diteurs. M. B. Roy et sa fille, Madame Louis Poinssot, laquelle a b6n6fici6 du concours 6clair6 et de la compétence arch6ologique de son savant mari, qui a

In: Arabica