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Electric field gradients at the nuclei of gallim and indium are determined by finite field calculations of the atomic energies as functions of the nuclear quadrupole moments. The four-component Dirac-Coulomb-Gaunt Hamiltonian serves as framework, and all electrons are correlated by Fock-space coupled cluster with single and double excitations or by single reference coupled cluster with approximate triples. Large, converged basis sets (e.g., 28s24p20d13f5g4h for In) and virtual spaces are used. Together with experimental nuclear quadrupole coupling constants, known with high precision, the calculated electric field gradients yield the nuclear quadrupole moments. For [sup.69]Ga, we get Q = 174(3) mb, in agreement with the earlier 171(2) mb obtained from molecular calculations. The [sup.115]In moment is Q = 772(5) mb, considerably lower than the previously accepted 810 mb, and in good agreement with the recent molecular value of 770(8) mb. Key words: nuclear quadrupole moments, gallium, indium, relativity, coupled cluster method. En faisant appel a des calculs de champ fini des energies atomiques en fonction des moments nucleaires quadripolaires, on a calcule les gradients de champs electriques des noyaux de gallium et d'indium. L'hamiltonien a quatre composants de Dirac-Coulom-Gaunt sert de reference et on a etabli une correlation entre tous les electrons a l'aide de l'agregat couple dans un espace de Fock avec des excitations simples ou doubles ou par l'agregat couple par reference simple avec des approximations de triplets. On a utilise de grands ensembles de bases convergents (tels 28s24p20d13f5h4h pour l'indium) et des espaces virtuels. En se basant sur les constantes de couplage quadripolaire nucleaire experimentales qui sont connues avec une grande precision, les gradients de champs electriques calcules ont permis de calculer les moments nucleaires quadripolaires. Pour le 69GA, on a obtenu une valeur de Q = 174(3) mb, en accord avec la valeur de 171(2) mb obtenue anterieurement par calculs moleculaires. Pour le 1151n, le moment est de Q = 772(5) mb, une valeur beaucoup plus basse que celle acceptee anterieurement, 810 mb, mais en bon accord avec la valeur moleculaire de 770(8) mb obtenue recemment. Mots-cles : moments quadripolaires nucleaires, gallium, indium, relativite, methode de l'agregat couple., [Traduit par la Redaction] Introduction The nuclear quadrupole moment (NQM) of [sup.115]In listed in Pyykko's 2001 compilation (2) is 810 mb (with 7% uncertainty), obtained by Belfrage et al. (3) [...]

Quantum dots with three-dimensional isotropic harmonic confining potentials and up to 60 electrons are studied. The Dirac-Coulomb Hamiltonian serves as a framework, so that relativistic effects are included, and electron correlation is treated at a high level by the Fock-space coupled cluster method, with single and double excitations summed to all orders. Large basis sets composed of spherical Gaussian functions are used. Energies of ground and excited states are calculated. The orbital order is 1s, 2p, 3d, 3s, 4f, 4p, 5g, ... , and closed-shell structures appear for 2, 8, 18, 20, 34, 40, and 58 electrons. Relativistic effects are negligible for low strengths of the harmonic potential and increase rapidly for stronger potentials. Breit contributions, coming from the lowest order relativistic correction to the interelectronic repulsion terms, are also studied. Correlation effects are significant for these systems, in particular for weak confining potentials and for small systems, where they constitute up to 6% of the total energies. Their relative weight goes down (although they increase in absolute value) for larger systems or confining potentials. Planned applications to quantum dots with impurities are discussed briefly. [ABSTRACT FROM AUTHOR]

The electric field gradient (EFG) at the gold nucleus is calculated using a finite field approach, to make the extraction of the nuclear quadrupole moment Q from experimental nuclear quadrupole coupling constants possible. The four-component Dirac-Coulomb Hamiltonian serves as the framework, 51 of the 79 electrons are correlated by the relativistic Fock-space coupled cluster method with single and double excitations, and the contribution of the Gaunt term, the main part of the Breit interaction, is evaluated. Large basis sets (up to 26s22p18d12f8g5h uncontracted Gaussians) are employed. Energy splittings of the 2D5/2 and 2D3/2 levels, rather than level shifts, are used to extract the EFG constants, as the former remain linear with Q up to 10-5 a.u., whereas the latter display significant nonlinearity even at Q=10-8 a.u. Larger Q values lead to larger energy changes and better precision. Excellent agreement (0.1%) is obtained between Q values derived from 2D5/2 and 2D3/2 data. Systematic errors connected with neglecting triple and higher excitations, truncating the basis and orbital active space, and approximating the Gaunt contribution are evaluated. The final value of Q(197Au) is 521(7) mb. It is lower than the muonic 547(16) mb and agrees within error bounds with the recent value of 510(15) mb obtained from molecular calculations. [ABSTRACT FROM AUTHOR]

Electric field gradients at the nuclei of halogen atoms are calculated using a finite field approach. The four-component Dirac-Coulomb Hamiltonian serves as the framework, all electrons are correlated by the relativistic Fock-space coupled cluster method with single and double excitations, and the Gaunt term, the main part of the Breit interaction, is included. Large basis sets (e.g., 28s24p21d9f4g2h Gaussian-type functions for I) are used. Combined with experimental nuclear quadrupole coupling constants, accurate estimates of the nuclear quadrupole moments are obtained. The calculated values are Q(35Cl)=-81.1(1.2) mb, Q(79Br)=302(5) mb, and Q(127I)=-680(10) mb. Currently accepted reference values [Pyykkö, Mol. Phys. 99, 1617 (2001)] are -81.65(80), 313(3), and -710(10) mb, respectively. Our values are lower for the heavier halogens, corroborating the recent work of van Stralen and Visscher [Mol. Phys. 101, 2115 (2003)], who obtained Q(127I)=-696(12) mb in a series of molecular calculations. [ABSTRACT FROM AUTHOR]

Electric field gradients at the nuclei of gallim and indium are determined by finite field calculations of the atomic energies as functions of the nuclear quadrupole moments. The four-component Dirac–Coulomb–Gaunt Hamiltonian serves as framework, and all electrons are correlated by Fock-space coupled cluster with single and double excitations or by single reference coupled cluster with approximate triples. Large, converged basis sets (e.g., 28s24p20d13f5g4h for In) and virtual spaces are used. Together with experimental nuclear quadrupole coupling constants, known with high precision, the calculated electric field gradients yield the nuclear quadrupole moments. For 69Ga, we get Q = 174(3) mb, in agreement with the earlier 171(2) mb obtained from molecular calculations. The 115In moment is Q = 772(5) mb, considerably lower than the previously accepted 810 mb, and in good agreement with the recent molecular value of 770(8) mb. [ABSTRACT FROM AUTHOR]

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