Parameterized optimized effective potential for atoms

The optimized effective potential equations for atoms have been solved by parameterizing the potential. The expansion is tailored to fulfill the known asymptotic behavior of the effective potential at both short and long distances. Both single configuration and multi configuration trial wave functions are implemented. Applications to several atomic systems are presented improving previous works. The results here obtained are very close to those calculated in either the Hartree-Fock and the multi configurational Hartree-Fock framework.Comment: 8 pages, 3 figure

Development of a battery of instruments for detailed measurement of health status in patients with COPD in routine care: the Nijmegen Clinical Screening Instrument

Contains fulltext : 80284.pdf (publisher's version ) (Closed access)PURPOSE: To compose a battery of instruments that provides a detailed assessment of health status (HS) in COPD but that is applicable and clinically meaningful in routine care. METHODS: In a previous study, we developed the Nijmegen Integral Assessment Framework (NIAF) that organizes existing tests and instruments by the sub-domains of HS they measure. Based on clinical and statistical criteria (correlation coefficients and Cronbach alpha's) we selected for each sub-domain instruments from the NIAF. A COPD-study group was used to determine c-scores, and two control groups were used to determine the score ranges indicating normal functioning versus clinically relevant problems for each sub-domain. Existing questionnaire completion software (TestOrganiser) was adapted to enhance clinical applicability. RESULTS: The NCSI measures eleven sub-domains of physiological functioning, symptoms, functional impairment, and quality of life. The TestOrganiser automatically processes the data and produces the graphical PatientProfileChart, which helps to easily interpret results. This envisages the problem areas and discrepancies between the different sub-domains. CONCLUSION: The NCSI provides a valid and detailed picture of a patient's HS within 15-25 min. In combination with the PatientProfileChart, the NCSI can be used perfectly in routine care as screening instrument and as a guide in patient-tailored treatment

Singly and doubly charged clusters of (S2) metals. Ab initio and model calculations on Mg+n and Mgn++n(n ≤ 5)

Accurate ab initio CI calculations on Mg+2 and Mg ++2 have been performed. The second appears to have a local minimum. Through a diabatization procedure, it was possible to define a simple model Hamiltonian spanned by products of atomic s2, s1 and s0 configurations. The model Hamiltonian includes instantaneous polarization energies (and three-body effects) and Coulombic repulsion of the holes in doubly charged clusters, and may be considered as treating one or two active holes in the polarizable s band. The model predicts linear Mg+3 and Mg++3 structures and nearly degenerate square and centred equilateral triangular structures for Mg+4 and Mg++4; Mg+5 and Mg++ 5 both present nearly degenerate minima of centred tetrahedron and centred square structures. The existence of such structures has been confirmed by UHF ab initio (gradient + force) calculations; it is shown however that single-determinantal approaches overestimate the bond lengths and unduly favour the centred structures; the Mg++5 minimum is 1.71 eV above the (Mg++ 3 + Mg+2) dissociation limit and 1.41 eV under the (3 Mg + 2 Mg+) dissociation limit. The vertical Ionisation Potentials (IP) have been calculated and it is shown that Mg+ 4, Mg+5 and Mg++5 may evaporate a neutral atom.Des calculs ab initio précis incluant la corrélation électronique ont été effectués pour Mg+2 et Mg++2. Le deuxième système présente un minimum local. A l'aide d'un procédé de diabatisation, on a pu définir un hamiltonien modèle simple porté par les produits des configurations atomiques s2 , s1 et s0. L'hamiltonien modèle inclut les effets de polarisation instantanée (ainsi que les effets à trois corps) et la répulsion coulombienne des charges positives pour les agrégats doublement chargés. Il peut être considéré comme une représentation de un ou deux trous actifs dans une bande s polarisable. Le modèle prédit que la structure la plus stable de Mg+3 et Mg++3 est linéaire, que les structures carrées et triangulaires centrées sont pratiquement équivalentes pour Mg+4 et Mg++4. Pour Mg +5 et Mg++5 existent également deux minima quasiment dégénérés : le tétraèdre centré et le carré centré. L'existence de telles structures a été confirmée par des calculs Hartree-Fock, par minimisation directe de l'énergie et calcul de la matrice des constantes de force pour la conformation optimale, mais on démontre que dans l'approche du modèle à particules indépendantes les longueurs de liaisons sont trop longues et les structures centrées sont trop stables. L'énergie du minimum de Mg ++5 est située à 1,71 eV au-dessus de la somme des énergies des systèmes Mg+3 et Mg+2. Les potentiels d'ionisation verticaux ont été calculés et on démontre que Mg +4, Mg+5 et Mg++5 peuvent évaporer un atome neutre

He(I) and He(II) Photoelectron Spectra and Pseudopotential ab Initio Calculations of Some Tetracoordinated Tin(IV) Derivatives

T h e gas-phase UV photoelectron (PE) spectra of Sn(CH3),C14-, ( n = 0-4) and of Sn(CH3),(NCS)4-, ( m = 2,3) are discussed with the aid of the results of pseudopotential a b initio calculations (extended basis sets with inclusion of 5d polarization functions and relativistic corrections for tin). The excellent numerical agreement between experimental and computed (Koopmans) ionization energies has allowed a reassignment of some published PE da t a and t h e discussion of t h e new spectra. T h e actual involvement of tin 5s ,5p, and 5d atomic orbitals into the valence MOs is also discussed. Both the theoretical and experimental data suggest t h e presence of strong xs,-cl interactions with significant contribution from Sn 5d AOs. As far as the NCS derivatives are concerned, both PE and theoretical da t a are in agreement with a largely ionic bon

Simple Two-Body Cation−Water Interaction Potentials Derived fromab Initio Calculations. Comparison to Results Obtained with an Empirical Approach

Ab initio calculations were performed on M(H2O)n systems, M being Li+, Na+, K+, Be2+, Mg2+, or Ca2+, with n = 1, 2, 4, or 6. For the most hydrated systems, parameters for the effective Lennard-Jones interaction between the cation and the water molecules were determined, so as to reproduce ab initio results. In order to compare our results to those obtained previously by J. Åqvist with a purely empirical approach, water−water interactions were assumed to be given by the TIP3P model. Different forms for the effective two-body interaction potential were tested. The best fits of ab initio data were obtained with a smooth r-7 repulsive and a classical r-4 attractive term, in addition to standard Coulombic interactions. Though better fits were obtained for alkaline cations than for alkaline-earth ones, only Be2+ obviously requires a more complicated form of the potential energy function.The corresponding parameters were tested with molecular dynamics simulations of cations in water solutions and with hydration free energy difference calculations, using the thermodynamic perturbation approach. Radial distribution functions consistent with experimental data were obtained for all cations. Free energy differences are obviously much more challenging. The most accurately reproduced value is the difference between the hydration free energies of Na+ and K+. This result is likely to be significant since effective interaction energies between Na+ or K+ and water molecules as obtained in Åqvist's and in the present work are found to be very similar, despite the fact that the corresponding sets of parameters were determined with completely different approaches

Uv Pe Spectra and Pseudopotential Abinitio Calculations On Trans-Pt(Pet3)2Cl2, Trans-Pt(Pet3)2Br2, Trans-Pt(Pet3)2I2 Complexes

The He I/He I1 excited photoelectron spectra of trans-Pt(PEt3)2X2 complexes (X = Cl, Br, I) are fully assigned with the aid of pseudopotential extended basis set ab initio calculations (including relativistic corrections for the Pt atom) on the whole series studied. Electronic reorganization energies upon ionization were estimated by means of a first-order perturbative treatment, which was revealed to be sufficiently accurate to allow a consistent interpretation of the experimental data. Moreover, the ab initio results provided new and interesting results that help to clarify the bonding scheme and its variation along the halide substituent series