Search results for "Calculation"
showing 10 items of 594 documents
Conformational Analysis of beta-Lactam-Containing Ferrocene Peptides
2009
The homochiral 3-amino-1-(4-methoxyphenyl)-4-phenyl-beta-lactam (≡ Alm) was conjugated with Boc-Ala giving Ala-Alm (9) after Boc-deprotection (Boc = tert-butoxycarbonyl, Ala = alanine). Coupling of FcCOOH (1) and Boc-Fca (10) with “ dipeptide” 9 resulted in the formation of FcCO-Ala-Alm (12) and the trisamide Boc-Fca-Ala-Alm (13), respectively (Fc = ferrocenyl, Fca = 1’ -aminoferrocene-1-carboxylic acid). The reactions were accomplished by the HOBt/EDC procedure and the products were obtained in good yields (HOBt = 1-hydroxybenzotriazole, EDC = N-(3-dimethylaminopropyl)-N’ -ethylcarbodiimide hydrochloride). Symmetrically 1, 1’ -disubstituted “ tetrapeptide” Fn(CO-Ala-Alm)2 (14) was prepared…
Density functional theory based screening of ternary alkali-transition metal borohydrides: a computational material design project.
2009
We present a computational screening study of ternary metal borohydrides for reversible hydrogen storage based on density functional theory. We investigate the stability and decomposition of alloys containing 1 alkali metal atom, Li, Na, or K M1; and 1 alkali, alkaline earth or 3d / 4d transition metal atom M2 plus two to five BH4 groups, i.e., M1M2BH42‐5, using a number of model structures with trigonal, tetrahedral, octahedral, and free coordination of the metal borohydride complexes. Of the over 700 investigated structures, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M1Al/ Mn/ FeBH44, Li/ NaZnBH43, and Na/ KNi/ CoBH43 alloys are …
Wannier90 as a community code: new features and applications
2019
Wannier90 is an open-source computer program for calculating maximally-localised Wannier functions (MLWFs) from a set of Bloch states. It is interfaced to many widely used electronic-structure codes thanks to its independence from the basis sets representing these Bloch states. In the past few years the development of Wannier90 has transitioned to a community-driven model; this has resulted in a number of new developments that have been recently released in Wannier90 v3.0. In this article we describe these new functionalities, that include the implementation of new features for wannierisation and disentanglement (symmetry-adapted Wannier functions, selectively-localised Wannier functions, s…
N-heterocyclic carbenes and parent cations: acidity, nucleophilicity, stability, and hydrogen bonding-Electrochemical Study and ab initio calculations
2016
N-Heterocyclic carbenes (NHCs) are widely used as organocatalysts. Their reactivity (and instability) is related to their basicity and nucleophilicity, which, in turn, are linked to their scaffold. NHCs can be generated by chemical deprotonation or electrochemical reduction of the parent azolium cations, NHCH+s. Cyclic voltammetry enabled the reduction potential of the NHCH+s to be determined; the reduction potential is related to the acidity of the NHCH+s and the oxidation potential of the NHCs, which is related to the nucleophilicity of the NHCs. It was thus possible to order different NHCH+s and NHCs by their acidity and nucleophilicity, respectively. A study on the stability of NHCs was…
Two C3-symmetric Dy3 III complexes with triple di-μ-methoxo-μ-phenoxo bridges, magnetic ground state, and single-molecule magnetic behavior
2014
Two series of isostructural C3-symmetric Ln3 complexes Ln3·[BPh4] and Ln3·0. 33[Ln(NO3)6] (in which LnIII=Gd and Dy) have been prepared from an amino-bis(phenol) ligand. X-ray studies reveal that LnIII ions are connected by one μ2-phenoxo and two μ3-methoxo bridges, thus leading to a hexagonal bipyramidal Ln3O5 bridging core in which LnIII ions exhibit a biaugmented trigonal-prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self-consistent field (CASSCF) calculations indicate that the magnetic coupling between the DyIII ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To redu…
Size-intensive decomposition of orbital energy denominators
2000
We introduce an alternative to Almlöf and Häser’s Laplace transform decomposition of orbital energy denominators used in obtaining reduced scaling algorithms in perturbation theory based methods. The new decomposition is based on the Cholesky decomposition of positive semidefinite matrices. We show that orbital denominators have a particular short and size-intensive Cholesky decomposition. The main advantage in using the Cholesky decomposition, besides the shorter expansion, is the systematic improvement of the results without the penalties encountered in the Laplace transform decomposition when changing the number of integration points in order to control the convergence. Applications will…
Multi-scale dynamics simulations of molecular polaritons: The effect of multiple cavity modes on polariton relaxation
2021
It is included two versions of this item: the Accepted Version which is already Open Access and the Published Version which is under an embargo period till 2022-03-09.
Pharmacogenetic Study of ABCB1 and CYP3A5 Genes During the First Year Following Heart Transplantation Regarding Tacrolimus or Cyclosporine Levels
2011
Pharmacogenetics explains part of the interindividual variability in drug responses. Many published works about the effects of single nucleotide polymorphisms (SNPs) on immunosuppressive drug blood levels present contradictory results. We evaluated the SNPs in ABCB1 (glycoprotein P) and CYP3A5 (metabolic enzyme) genes, seeking correlate them with tacrolimus or cyclosporine levels during the first year after heart transplantation. One blood sample was obtained from each of 41 patients: 26 treated with cyclosporine and 15 with tacrolimus. We characterize the SNPs rs1045642, 1128503, 2032582, 2235013, 2235033, 2229109, 3213619, 9282564 in ABCB1 and rs10264272, 776746 in CYP3A5 genes using the …
Resistance simulations for junctions of SW and MW carbon nanotubes with various metal substrates
2011
Abstract This theoretical study focuses on junctions between the carbon nanotubes (CNTs) and contacting metallic elements of a nanocircuit. Numerical simulations on the conductance and resistance of these contacts have been performed using the multiple scattering theory and the effective media cluster approach. Two models for CNT-metal contacts have been considered in this paper: a) first principles “liquid metal” model and b) semi-empirical model of “effective bonds” based on Landauer notions on ballistic conductivity. Within the latter, which is a more adequate description of chirality effects, we have simulated both single-wall (SW) and multi-wall (MW) CNTs with different morphology. Res…
Progress in the benchmark exercise for analyzing the lithiate breeder pebble bed thermo-mechanical behaviour
2006
The Helium Cooled Pebble Bed (HCPB) Blanket is one of the reference concepts for the European Breeding Blanket Programme for DEMO. In the reference blanket module, alternate layers of lithiated ceramics and beryllium pebbles act, respectively, as tritium breeder and neutron multiplier. The thermo-mechanical behaviour of both the pebble beds and their performances in reactor relevant conditions are also dependent on the pebble size and cell geometries (bed thickness, pebble packing factor, bed thermal conductivity). Therefore, in the EU Fusion Technology Programme, several out-of-pile experimental test campaigns have been performed to determine these behaviours. Theoretical calculations have…