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Papers by Ricardo Celeste

Research paper thumbnail of On the helium ground-state Hartree-Fock energy

Chemical Physics Letters, 1991

The Hartree-Fork limit for the ground state of the He atom is rediscussed on the basis of the gen... more The Hartree-Fork limit for the ground state of the He atom is rediscussed on the basis of the generator-coordinate Hartree-Fock method and the Laplace transform. A numerical solution is implemented which leads to a value of 73 x 1O-'2 hartree below the commonly accepted limit.

Research paper thumbnail of On the Use of an Interpolation Approach for the Choice of Gaussian Polarization Functions

Journal of the Brazilian Chemical Society

In this work, we tested a linear interpolation approach in order to select polarization functions... more In this work, we tested a linear interpolation approach in order to select polarization functions (exponents) to be used with Gaussian basis sets. The Gaussian primitive functions were generated here for Ga to Kr and also for Sc to Cu. The general contraction method was used for the construction of contracted Gaussian basis sets of 6Z and 7Z quality. Polarization functions were added to the contracted bases by explicit optimization and also by interpolation of exponents. The performance of the contracted basis sets, augmented with polarization functions obtained by interpolation, was tested with molecular configurations interaction single and double excitations (CISD) and density functional theory (DFT) calculations for the systems Se, Se 2 , Se 6 , Ge 2 , CrH and FeH. The outcomes obtained in this work with interpolated polarization functions agreed very well with the ones augmented with polarization functions obtained by explicit optimization. The interpolation methodology presented here is useful to generate polarization functions for any Gaussian basis set in different series of atoms of the periodic table.

Research paper thumbnail of Neutral atoms and ion energies, accurate ionization potential, and electron affinities by polynomial generator coordinate Hartree–Fock method

TURKISH JOURNAL OF CHEMISTRY

We have developed accurate Gaussian basis functions obtained with the polynomial generator coordi... more We have developed accurate Gaussian basis functions obtained with the polynomial generator coordinate Hartree-Fock (p-GCHF) method for H, Zn, and Ga-Kr atoms. These basis sets have been applied in the calculation of nonrelativistic energies for neutral atoms, monovalent cations, monovalent anions, ionization potential (IP), and electron affinity (EA), with the objective of proving the quality of the basis set generated by the p-GCHF method. The total energies calculated for neutral atoms and monovalent cations and respective IP were minimally affected by the addition of polarization functions and their precision was comparable to the values reported in the literature. The relative errors were lower than 6.0 × 10 −5 % and 7.0 × 10 −5 % for neutral atoms and monovalent cations, respectively. The IP results were strictly equal to numerical Hartree-Fock (NHF) calculations and comparable to some experimental values. For monovalent anions, the nonrelativistic total energies were better than the Slater-type functions results and the relative errors were lower than 0.05% when compared to NHF. The EA results were the same as those obtained with NHF calculations reported in the literature for heavier elements. For IP and EA, our results followed the same periodic tendency when compared with experimental data.

Research paper thumbnail of Accurate Gaussian basis sets for atomic and molecular calculations obtained from the generator coordinate method with polynomial discretization

Journal of Molecular Modeling, 2015

Accurate Gaussian basis sets for atoms from H to Ba were obtained by means of the generator coord... more Accurate Gaussian basis sets for atoms from H to Ba were obtained by means of the generator coordinate Hartree-Fock (GCHF) method based on a polynomial expansion to discretize the Griffin-Wheeler-Hartree-Fock equations (GWHF). The discretization of the GWHF equations in this procedure is based on a mesh of points not equally distributed in contrast with the original GCHF method. The results of atomic Hartree-Fock energies demonstrate the capability of these polynomial expansions in designing compact and accurate basis sets to be used in molecular calculations and the maximum error found when compared to numerical values is only 0.788 mHartree for indium. Some test calculations with the B3LYP exchange-correlation functional for N2, F2, CO, NO, HF, and HCN show that total energies within 1.0 to 2.4 mHartree compared to the cc-pV5Z basis sets are attained with our contracted bases with a much smaller number of polarization functions (2p1d and 2d1f for hydrogen and heavier atoms, respectively). Other molecular calculations performed here are also in very good accordance with experimental and cc-pV5Z results. The most important point to be mentioned here is that our generator coordinate basis sets required only a tiny fraction of the computational time when compared to B3LYP/cc-pV5Z calculations.

Research paper thumbnail of On the helium ground-state Hartree-Fock energy

Chemical Physics Letters, 1991

The Hartree-Fork limit for the ground state of the He atom is rediscussed on the basis of the gen... more The Hartree-Fork limit for the ground state of the He atom is rediscussed on the basis of the generator-coordinate Hartree-Fock method and the Laplace transform. A numerical solution is implemented which leads to a value of 73 x 1O-'2 hartree below the commonly accepted limit.

Research paper thumbnail of On the Use of an Interpolation Approach for the Choice of Gaussian Polarization Functions

Journal of the Brazilian Chemical Society

In this work, we tested a linear interpolation approach in order to select polarization functions... more In this work, we tested a linear interpolation approach in order to select polarization functions (exponents) to be used with Gaussian basis sets. The Gaussian primitive functions were generated here for Ga to Kr and also for Sc to Cu. The general contraction method was used for the construction of contracted Gaussian basis sets of 6Z and 7Z quality. Polarization functions were added to the contracted bases by explicit optimization and also by interpolation of exponents. The performance of the contracted basis sets, augmented with polarization functions obtained by interpolation, was tested with molecular configurations interaction single and double excitations (CISD) and density functional theory (DFT) calculations for the systems Se, Se 2 , Se 6 , Ge 2 , CrH and FeH. The outcomes obtained in this work with interpolated polarization functions agreed very well with the ones augmented with polarization functions obtained by explicit optimization. The interpolation methodology presented here is useful to generate polarization functions for any Gaussian basis set in different series of atoms of the periodic table.

Research paper thumbnail of Neutral atoms and ion energies, accurate ionization potential, and electron affinities by polynomial generator coordinate Hartree–Fock method

TURKISH JOURNAL OF CHEMISTRY

We have developed accurate Gaussian basis functions obtained with the polynomial generator coordi... more We have developed accurate Gaussian basis functions obtained with the polynomial generator coordinate Hartree-Fock (p-GCHF) method for H, Zn, and Ga-Kr atoms. These basis sets have been applied in the calculation of nonrelativistic energies for neutral atoms, monovalent cations, monovalent anions, ionization potential (IP), and electron affinity (EA), with the objective of proving the quality of the basis set generated by the p-GCHF method. The total energies calculated for neutral atoms and monovalent cations and respective IP were minimally affected by the addition of polarization functions and their precision was comparable to the values reported in the literature. The relative errors were lower than 6.0 × 10 −5 % and 7.0 × 10 −5 % for neutral atoms and monovalent cations, respectively. The IP results were strictly equal to numerical Hartree-Fock (NHF) calculations and comparable to some experimental values. For monovalent anions, the nonrelativistic total energies were better than the Slater-type functions results and the relative errors were lower than 0.05% when compared to NHF. The EA results were the same as those obtained with NHF calculations reported in the literature for heavier elements. For IP and EA, our results followed the same periodic tendency when compared with experimental data.

Research paper thumbnail of Accurate Gaussian basis sets for atomic and molecular calculations obtained from the generator coordinate method with polynomial discretization

Journal of Molecular Modeling, 2015

Accurate Gaussian basis sets for atoms from H to Ba were obtained by means of the generator coord... more Accurate Gaussian basis sets for atoms from H to Ba were obtained by means of the generator coordinate Hartree-Fock (GCHF) method based on a polynomial expansion to discretize the Griffin-Wheeler-Hartree-Fock equations (GWHF). The discretization of the GWHF equations in this procedure is based on a mesh of points not equally distributed in contrast with the original GCHF method. The results of atomic Hartree-Fock energies demonstrate the capability of these polynomial expansions in designing compact and accurate basis sets to be used in molecular calculations and the maximum error found when compared to numerical values is only 0.788 mHartree for indium. Some test calculations with the B3LYP exchange-correlation functional for N2, F2, CO, NO, HF, and HCN show that total energies within 1.0 to 2.4 mHartree compared to the cc-pV5Z basis sets are attained with our contracted bases with a much smaller number of polarization functions (2p1d and 2d1f for hydrogen and heavier atoms, respectively). Other molecular calculations performed here are also in very good accordance with experimental and cc-pV5Z results. The most important point to be mentioned here is that our generator coordinate basis sets required only a tiny fraction of the computational time when compared to B3LYP/cc-pV5Z calculations.