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  • 1
    Electronic Resource
    Electronic Resource
    A path integral ground state method (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 1366-1371 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ground state expectation values are obtained by using a path integral ground state Monte Carlo method. The method allows calculations of ground state expectation values without the extrapolations often used with Green's function and diffusion Monte Carlo methods. We compare our results with those of Green's function Monte Carlo by calculating some ground state properties of the van der Waals complex He2Cl2 as well as the infinite systems liquid and solid 4He. Advantages and disadvantages of the present method with respect to previous ones are discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481926
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  • 2
    Electronic Resource
    Electronic Resource
    Quadratic diffusion Monte Carlo and pure estimators for atoms (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 5956-5962 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The implementation and reliability of a quadratic diffusion Monte Carlo method for the study of ground-state properties of atoms are discussed. We show in the simple yet nontrivial calculation of the binding energy of the Li atom that the method presented is effectively second-order in the time step. The fulfillment of the expected quadratic behavior relies on some basic requirements of the trial wave function used for importance sampling, in the context of the fixed-node approximation. Expectation values of radial operators are calculated by means of a pure estimation based on the forward walking methodology. It is shown that accurate results without extrapolation errors can be obtained with a pure algorithm, explicitely reported, that can be easily implemented in any previous diffusion Monte Carlo program. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1446847
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  • 3
    Electronic Resource
    Electronic Resource
    Constraint dynamics for quantum Monte Carlo calculations (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 44-47 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe how to apply classical constraint dynamics to problems in diffusion Monte Carlo. We apply the method to rigid and nonrigid water molecules with an internal rotational degree of freedom. The method is applicable to a wide variety of problems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481771
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  • 4
    Electronic Resource
    Electronic Resource
    Correlated two-electron momentum properties for helium to neon atoms (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5721-5727 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Two-electron properties in momentum space for the atoms helium to neon have been calculated starting from explicitly correlated wave functions. The different integrals involved in the calculation have been evaluated by using the Monte Carlo algorithm. In particular, the spherically averaged interelectronic momentum distribution, γ(2)(p12),its radial moments 〈p12n〉, with n=−2 to +3, the expectation value 〈p1⋅p2〉, and both the electron–electron coalescence, γ(2)(0), and counterbalance, Γ(2)(0), densities have been calculated. A systematic study of the electronic correlation has been performed by comparing the correlated results with the corresponding Hartree–Fock ones. Finally an analysis of the structure of the interelectronic momentum distribution in terms of its parallel and antiparallel components has been carried out. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478470
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  • 5
    Electronic Resource
    Electronic Resource
    A variational Monte Carlo study of the 2s-2p near degeneracy in beryllium, boron, and carbon atoms (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 3346-3351 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We apply the variational Monte Carlo method to study the beryllium, boron, and carbon atoms. An explicitly correlated wave function is used in order to include the dynamic correlation among the electrons. The nondynamic correlation due to the 2s-2p near degeneracy effect present in these atoms is taken into account by using a multideterminant wave function. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476929
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  • 6
    Electronic Resource
    Electronic Resource
    Correlated Monte Carlo electron-pair density for the atoms helium to neon (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 7075-7084 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Monte Carlo method to obtain the electron-pair density for the atoms helium to neon has been applied. The wave functions of Schmidt and Moskowitz [J. Chem. Phys. 93, 4172 (1990)] to take into account the dynamic correlation among the electrons have been used. For the atoms Be, B and C we have considered the nondynamic correlation due to the near degeneracy 2s−2p by means of a configuration interaction wave function and for Li and Be we have also varied the central part of the wave function. A study of the differences between the correlated and the Hartree–Fock results has been carried out. Finally we have also calculated the interelectronic moments, 〈r12n〉, and the value of the electron pair density at the coalescence point for all the atoms considered. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477390
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  • 7
    Electronic Resource
    Electronic Resource
    Variational calculation of some S-states of Coulomb three-body systems (2001)
    Springer
    The European physical journal 13 (2001), S. 201-206 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 36.10.Dr Positronium, muonium, muonic atoms and molecules – 31.25.-v Electron correlation calculations for atoms and molecules – 31.15.Pf Variational techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A generalized Hylleraas-type basis set with three nonlinear parameters is proposed to study three-body systems interacting via coulomb forces within the framework of non-relativistic quantum mechanics. This basis set improves the rate of convergence with respect to previous ones, specially for non-symmetric systems and excited states of two electron atoms. Accurate binding energies and other properties for S-states of helium-like ions, muonic molecules and the positronium negative ion are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170267
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  • 8
    Electronic Resource
    Electronic Resource
    Precise variational calculation of some S-states of Coulomb three-body systems with two identical particles (1998)
    Springer
    The European physical journal 2 (1998), S. 181-190 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 36.10.Dr Positronium, muonium, muonic atoms and molecules - 31.10.+z Theory of electronic structure, electronic transitions, and chemical binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A generalized Hylleraas basis set with two nonlinear parameters is used to study three-body systems with two equal masses interacting via coulomb forces within the framework of non-relativistic quantum mechanics. Accurate variational bounds for the ground state of some of these systems are obtained improving the rate of convergence of the calculation with respect to an usual Hylleraas basis set. A study of the interparticle densities is also carried out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050128
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  • 9
    Electronic Resource
    Electronic Resource
    Hartree-Fock wave functions with a modified GTO basis for atoms (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 59-64 
    Details
    ISSN: 0020-7608
    Keywords: Atomic structure ; Hartree-Fock ; modified Gaussian orbitals ; momentum density ; single-particle density ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have solved the atomic Hartree-Fock equations by using the algebraic approach, expanding the single-particle radial wave function in terms of a modified Gaussian type orbitals (GTOs) basis. Several atomic properties such as Kato's cusp condition for the electron density or the correct asymptotic behavior of the electron momentum density distribution are accurately verified. Additionally the energy of the atomic ground state can be obtained by using a smaller number of basis functions than in standard GTO expansions. This study has been performed for several atoms of the first three rows.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 59-64, 1997
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Factored wave function for bound S-type states of two-electron atomic systems (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 68 (1998), S. 405-413 
    Details
    ISSN: 0020-7608
    Keywords: S-states of two electron atoms ; correlated basis function ; factored wave functions ; one- and two-body densities ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple and accurate variational wave function in which the dependence in the interelectronic distance is factored is proposed to describe S-type states of two-electron atomic systems. We introduce a parameterization which generalizes the previous ones used in this same framework and which allows us to obtain in a simple way the wave function of both symmetric and antisymmetric excited states. We performed a systematic analysis of some exact properties such as the virial theorem and the cusp conditions and a study of both the one- and two-body densities. Finally, a comparison among the different correlation functions for these states was performed for helium.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 405-413, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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