Theoretical study of the low‐lying states of trans‐1,3‐butadiene

We present extensive ab initio calculations on the low‐lying electronic states of trans‐1,3‐butadiene within the multireference configuration interaction (MRCI) framework by selecting the configurations with a perturbative criterion. The X 1Ag ground state and 1 3Bu, 1 3Ag, 2 1Ag, and 1 1Bu valence excited states have been calculated at a fixed geometry. The results obtained are in good agreement with previous experimental and calculated values, and could help to understand polyene spectroscopy, photochemistry, and photophysics. The advantages of a MRCI method where the most important contributions to the total MRCI wave function, perturbatively selected, are treated variationally, and the remaining terms are evaluated by means of a perturbational approach, are also discussed. Furthermore, a criterion in order to build a correlation‐consistent configuration interaction space is stated and, therefore, a reliable approximation to achieve accurate energy differences is obtained. Several monoelectronic molecular‐orbital basis functions are tried in order to select the most adequate to describe each [email protected] ; [email protected] ; [email protected]

Elementary presentation of self‐consistent intermediate Hamiltonians and proposal of two totally dressed singles and doubles configuration interaction methods

Intermediate Hamiltonians are effective Hamiltonians which are defined on an N‐dimensional model space but which only provide n<N exact eigenvalues and the projections of the corresponding eigenvectors onto the model space. For a single root research, the intermediate Hamiltonian may be obtained from the restriction of the Hamiltonian to the model space by an appropriate, uniquely defined dressing of the diagonal energies or of the first column. Approximate self‐consistent dressings may be proposed. The simplest perturbative form gives the same result as the original 2nd order intermediate Hamiltonian or the ‘‘shifted Bk’’ technique but it is of easier implementation. Self‐consistent inclusion of higher order exclusion principle violating corrections greatly improves the results, especially for nearly degenerate problems, as shown on several illustrative applications. Possible generalizations to enlarged or reduced model spaces are [email protected] ; [email protected]

Towards an accurate molecular orbital theory for excited states : Ethene, butadiene, and hexatriene

A newly proposed quantum chemical approach for ab initio calculations of electronic spectra of molecular systems is applied to the molecules ethene, trans‐1,3‐butadiene, and trans‐trans‐1,3,5‐hexatriene. The method has the aim of being accurate to better than 0.5 eV for excitation energies and is expected to provide structural and physical data for the excited states with good reliability. The approach is based on the complete active space (CAS) SCF method, which gives a proper description of the major features in the electronic structure of the excited state, independent of its complexity, accounts for all near degeneracy effects, and includes full orbital relaxation. Remaining dynamic electron correlation effects are in a subsequent step added using second order perturbation theory with the CASSCF wave function as the reference state. The approach is here tested in a calculation of the valence and Rydberg excited singlet and triplet states of the title molecules, using extended atomic natural orbital (ANO) basis sets. The ethene calculations comprised the two valence states plus all singlet and triplet Rydberg states of 3s, 3p, and 3d character, with errors in computed excitation energies smaller than 0.13 eV in all cases except the V state, for which the vertical excitation energy was about 0.4 eV too large. The two lowest triplet states and nine singlet states were studied in butadiene. The largest error (0.37 eV) was found for the 2 1Bu state. The two lowest triplet and seven lowest singlet states in hexatriene had excitation energies in error with less than 0.17 [email protected] ; [email protected] ; [email protected]

The chemical bonds in CuH, Cu2, NiH, and Ni2 studied with multiconfigurational second order perturbation theory

The performance of multiconfigurational second order perturbation theory has been analyzed for the description of the bonding in CuH, Cu2, NiH, and Ni2. Large basis sets based on atomic natural orbitals (ANOS) were employed. The effects of enlarging the active space and including the core‐valence correlation contributions have also been analyzed. Spectroscopic constants have been computed for the corresponding ground state. The Ni2 molecule has been found to have a 0+g ground state with a computed dissociation energy of 2.10 eV, exp. 2.09 eV, and a bond distance of 2.23 Å. The dipole moments of NiH and CuH are computed to be 2.34 (exp. 2.4±0.1) and 2.66 D, [email protected] ; [email protected] ; [email protected]

Polarization by the effect of a small torsional change in the benzothiazole (A)-benzobisthiazole (B) oligomer A-B13-A

Abstract: We use a method for the calculation of the molecular dipole ( µ) and quadrupole (θ) moments and dipole-dipole (α), dipole-quadrupole ( A) and quadrupole-quadrupole ( C) polarizabilities which we have successfully applied to the benzothiazole (A)benzobisthiazole (B) linear oligomer A-B13-A. Two model rotational isomers have been characterized: (1) the fully-planar (000) conformation; and (2) a rotational isomer with each unit rotated in the range 1 − 10 ° in the same direction (+++). For isomer 000, µ is smaller than for +++. The calculation of α, A and C has been carried out by the interacting induced dipoles polarization model that calculates tensor effective anisotropic point polarizabilities (method of Applequist et al.). The values of A are specially sensitive to µ which varies under rotation. This fact explains the great values of Ax, xx for the +++ polar isomer. It is found that small torsional changes can enhance solubility by a clear increasing of the hydrophilic accessible surface area. However, the torsion of the oligomer varies the value of µ and so modifies α, C, and, specially, A. For conformer +++, polarization effects occur even when each unit is rotated only φ = 1°. The observed effect is an increase in µ and, hence, in α, C, and, specially, A

Selected dissociation‐ and correlation‐consistent configuration interaction by a perturbative criterion

We propose a perturbative criterion to select the most important dissociation‐ or correlation‐consistent type of contributions to perform generalized valence bond‐configuration interaction (GVB‐CI) calculations, dissociation‐consistent configuration interaction (DCCI) or correlation‐consistent configuration interaction (CCCI) approach, respectively. The procedure presented is computationally less demanding than the CCCI proposed by Goddard and co‐workers. To ensure the distance consistency of the MOs used, the nonvalence virtual orbitals are obtained by a projection technique. The results obtained for a few test calculations show the ability of the suggested approach to get close results to full CI, DCCI, and CCCI values using a small CI expansion. It seems to be a promising way to treat correlation changes in large molecular systems which would be inaccessible by other [email protected] ; [email protected]

Los jóvenes ante su salud

Este informe trata de contribuir a la difusión de los resultados de los estudios realizados a partir de los dos sistemas de información de la Consejería de Sanidad de la Comunidad de Madrid, el SIVFRENT (Sistema de Vigilancia de Factores de Riesgo de las Enfermedades No Transmisibles) y el SISS (Sistema de Información de Indicadores de Salud de Carácter Sociocultural). Se dirige a los profesionales y organizaciones que trabajan con jóvenes, para que puedan disponer de la mayor información posible sobre las concepciones de salud de este grupo y puedan comprender mejor sus actitudes. El documento se divide en dos partes; en la primera parte, realizada a partir de la información del SISS, se exponen las representaciones sociales de los jóvenes sobre la salud; y en la segunda parte, realizada con los datos del SIVFRENT, se presenta la posición de los jóvenes respecto a las enfermedades y/o determinados hábitos de salud, así como su actitud y comportamientos en cuanto a la prevención del riesgo de accidente. En ambas partes, los datos se acompañan de información recogida en diferentes estudios cualitativos realizados por la Consejería de Sanidad y Servicios Sociales. Finalmente, se incluyen las Conclusiones y Estrategias de promoción de la salud.MadridES