Electronic confinement effects on the reaction field type calculations of solvent effects

Int J of Quantum Chemistry

Zorrilla

Fernández

2014

Self Cite

We introduce a new type of spatially restricted basis function (zero beyond a characteristic r 0 value of the radial coordinate) that makes it possible to obtain, in nonconfined systems, similar results to STO functions. This is important because the use of this kind of functions enables the exact application a sort of zero differential overlap approximation to calculate properties of large systems. Our functions are a modification of the BO-xZ box orbitals introduced by Lepetit et al. First, we replaced these orbitals by a function that is easier to obtain and generalize, that we named "simplified box orbital" (SBO), and we have shown some advantages of the SBO over BO and standard STO functions. Second, we obtained Gaussian developments for both the original BO orbitals and the new SBO orbitals. In this way, it becomes possible to manage our SBO orbitals with standard quantum chemistry software like GAUS-SIAN or similar programs.

Section: Advantages Of the Sbo Over Numerical Atomic Orbitalsmentioning

confidence: 99%

Section: Advantages Of the Sbo Over Numerical Atomic Orbitalsmentioning

confidence: 99%

Section: Advantages Of the Sbo Over Numerical Atomic Orbitalsmentioning

confidence: 99%

“…We have also modified the UCA‐CMC program, initially developed for the research presented in Ref. , to operate with this kind of basis functions.…”

Section: Obtaining Gaussian Expansions For Spatially Restricted Functmentioning

confidence: 99%

\sum_{p = 1}^{m} C_{p} {(r_{p} - r)}^{3} ≅ \sum_{λ = 1}^{n} a_{λ} \exp (- b_{λ} r^{2})

…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Simplified box orbitals: A spatially restricted alternative to the slater‐type orbitals

Int J of Quantum Chemistry

Zorrilla

Fernández

2014

Self Cite

Simplified Box Orbitals (SBO) for H To Ar atoms: Exact expressions, SBO-3G approximations, and relations with the ZDO approximation

Zorrilla

Sánchez‐Márquez

et al. 2016

Int. J. Quantum Chem.

Self Cite

Jes us S anchez-M arquez, and Manuel Fern andez-N uñez Simplified Box Orbitals (SBO) are a kind of spatially restricted basis functions. SBOs have a similar use and value to Slater functions but, because they fulfill a version of the zerodifferential overlap approximation, they allow for a drastic reduction in the number of two-electron integrals to be calculated when dealing with huge systems, and they seem to be specially adapted to study confined systems such as molecules in solution. In a previous study, the mathematical shape of SBOs was discussed and the necessary parameters were obtained by means of the variational method. In the present study, the parameters of each SBO were obtained by applying the condition that it is as similar as possible to the STO that would be used in a basis set without spatial restrictions. We have developed a method to achieve this likeness and deduced simple formulas to describe all the SBOs of any atom. We also present the SBO-3G expansions of the SBOs obtained, making it possible to use these SBOs with standard quantum chemistry calculation software. Simple formulas were also deduced to directly write the SBOs and SBO-3G corresponding to the atoms with a Z value of between 1 and 18. Finally, as a first example of the usefulness of this kind of functions, an optimized SBO-3G basis set is proposed for atoms from H to Cl in molecules.

Spatially restricted Double Z‐Simplified Box Orbital basis sets: Optimization and comparison with some standard basis sets

Int J of Quantum Chemistry

Sánchez‐Márquez

Torres

et al. 2019

Self Cite

As part of previous studies, we introduced a new type of basis function named Simplified Box Orbitals (SBOs) that belong to a class of spatially restricted functions which allow the zero differential overlap (ZDO) approximation to be applied with complete accuracy. The original SBOs and their Gaussian expansions SBO-3G form a minimal basis set, which was compared to the standard Slater-type orbital basis set (STO-3G). In the present paper, we have developed the SBO basis functions at double-zeta (DZ) level, and we have assessed the option of expanding the SBO-DZ as a combination of Gaussian functions. Finally, we have determined the quality of the new basis set by comparing the molecular properties calculated with SBO-nG with those achieved with some standard basis sets. K E Y W O R D S ab-initio calculations, box orbitals, confined systems, Gaussian expansion, spatially restricted basis functions 1 | INTRODUCTION: SIMPLIFIED BOX ORBITAL AND SIMPLIFIED BOX ORBITAL-nG FUNCTIONS Spatially restricted functions are distinguished as having a value of zero from a certain distance to the center to which they are referred:r > r o ) χ(r,θ,ϕ) = 0. This characteristic makes the integrals S pq , H pq , and (pq|rs) zero when the distance between the centers of the two basis functions χ p and χ q is higher than the sum of the radii associated with those two functions. Therefore, it leads to simplifications analogous to those of the zero differential overlap (ZDO) approximation of the semiempirical methods, but in a completely ab-initio context. This advantage has been proven to be useful for improving the computing calculations as shown by the results obtained, for example, with Ramp functions. [1][2][3] In previous studies based on the pioneering work of Lepetit et al. [4] and Fernández Rico et al., [5][6][7][8] we developed a valid spatially restricted basis set for performing calculations on molecules with atoms from H to Kr, but at "single-zeta level." [9][10][11] In this paper we have developed an Simplified Box Orbital (SBO) basis set at "double-zeta level," which allows calculations to be performed with similar or higher precision than the well-known standard basis set 6-311G(d) of Pople et al. [12] An SBO is a spatially restricted function achieved through the linear combination of terms (r − r o ) 3n for the interval 0 < r < r o and with the value of zero outside this interval.with the radial part defined as a piecewise function: