The electron density distribution in CN−, LiCN and LiNC. The use of minimal and extended basis set SCF calculations

Electron density maps are reported for the CN−ion and the LiCN and LiNC molecules, calculated from molecular wave-functions near the Hartree-Fock limit. The electron density distribution derived from CNDO/ 2 wavefunctions does not resemble the ab initio results. The ultimate ability of a minimal basis set to represent the electron density near the Hartree-Fock limit, has been tested. The requirement of N-representability of the trial electron density has been satisfied. It is found that the molecular valence density cannot be reproduced to a satisfactory extent by a minimal set of Slater orbitals, even when the exponents of the basis orbitals are optimized

The crystal structure of urea oxalic acid (2:1)

The crystal structure of urea oxalic acid, 2[CO(NH2)2].(COOH)2 has been determined using three-dimensional X-ray data, collected on an automatic diffractometer. The space group is P21/c. The lattice constants are: a = 5.058 (3), b = 12.400 (3), c = 6.964 (2) A, fl= 98"13 (7) °. The number of molecules in the unit cell is two. The structure consists of layers of urea and oxalic acid molecules held together by hydrogen bonds. The positions of all hydrogen atoms have been found. The compound is not a uronium salt

An electron density study of sodium sulfanilate dihydrate at 78 K

The crystal structure of sodium sulfanilate dihydrate has been redetermined from single-crystal X-ray data collected at 78 K. Separate least-squares refinements were performed on the low-order data, the high-order data and the entire data set. The nonplanarity of the amino group has been reconfirmed. Difference density maps, based on the atomic parameters from the high-order refinement, are interpreted in terms of bonding effects. An analysis of the charge distribution led to net charges of -0.37 (4), +0-07 (4) and +0.15 (4) e for the sulfanilate group, Na atom and hydrate molecules respectively

Les bibliothèques vivantes

Outil de la lutte contre lexclusion, la bibliothèque vivante, expérimentée dès 2000 au Danemark, doit, pour devenir un véritable vecteur dinclusion, évoluer et dépasser sa nature événementielle, et notamment en associant les publics de façon pérenne à la co-construction de la bibliothèque

Tous à Greenwich Village !

Quand, à l\u27initiative d\u27une bibliothèque, un quartier revit ses grandes heures : les anciens racontent, les plus jeunes recueillent leurs paroles, et tout le monde partage la mémoire qui revit, bien au-delà du cercle des habitants. Amateurs de poésie, de musique folk, de jazz, de peinture du monde entier, c\u27est pour vous : écoutez, réagissez, participe

La participation en bibliothèque

La participation : une nouvelle tendance pour faire de son établissement une véritable bibliothèque de son temps ? Mieux : en se saisissant enfin d\u27une vieille notion, les bibliothèques ne se mettent pas au goût du jour, mais se projettent au-delà dans de nouveaux lendemains