Choice of atomic orbitals to evaluate sensitive properties of molecules: An example of NMR chemical shifts

Abstract

Now ab initio or density functional theory (DFT) molecular property calculations over a Slater-type orbital basis are available in several software packages. In this work, the relative merits of various exponential-type orbitals (ETOs) are investigated for solving problems of interest to nuclear magnetic resonance (NMR), while showing how they are related mathematically. The preferred ETOs will be shown to be the hydrogenic orbitals and similar Coulomb Sturmians. Slater-type functions (STFs) will be compared with them, and suitable equivalent (seldom used) combinations given. The correct shielding of the nucleus, resulting from radial factors of hydrogenic orbitals, is finally shown to be essential in the evaluation of precise nuclear shielding tensors for NMR spectroscopy of molecules using ab initio or DFT methods.

Suitable basis sets for accurate NMR chemical shift calculations: an application to in vivo studies of benzothiazole metabolites

“…The content of this table is original and based on the previous work of the author (Hoggan, 2004) i.e. geometries are re-optimized from the co-ordinates of (Hoggan, 2004). …”

“…Multiple zeta basis sets may be used, on condition the appropriate constraints are applied to certain 1s and 2s elements in the set to include a 1s with the exponent required in the 2s and the appropriate coefficients to obtain a factor 2-r overall. This point has been tested successfully with STOP (2003) (Hoggan, 2004) in particular following PhD work by L. Berlu (Berlu, 2003), supervised by the author.…”

Polarizabilities, Hyperpolarizabilities and Analogous Magnetic Properties

“…Hoggan 255,256 advocates the use of hydrogenic atomic orbitals for the calculation of sensitive molecular properties such as NMR chemical shifts. The correct shielding of the nucleus, as given by the radial hydrogenic factors, is essential.…”

Cusps and derivatives for wave‐functions expanded in Slater orbitals: A density study

“…The limiting behaviour of Gaussian basis sets is a zero derivative at the nucleus (horizontal tangent). This, in itself, may cause problems for NMR shielding tensor calculations 27 and QMC local energies. The behavior of quality Gaussian basis sets, such as aug‐cc‐pvtz, is nevertheless quite satisfactory except very close to the nucleus.…”