Influence of local electrical fields on the properties and structure of carbon monoxide

Computational methods are presented which are open-ended with respect to gaussian basis functions (s,p,d,f,g,h,$\...$) for one and two-electron integrals. A universal computational approach for evaluating one-electron integrals over gaussian basis functions for general operators of the form$$\rm x\sp{k\sb x}y\sp{k\sb y}z\sp{k\sb z}\left\{\left({\partial\over\partial x\prime}\right)\sp{l\sb x}\left({\partial\over\partial y\prime}\right)\sp{l\sb y}\left({\partial\over\partial z\prime}\right)\sp{l\sb z}{1\over r\prime}\right\}\cr\left({\partial\over\partial x}\right)\sp{m\sb x}\left({\partial\over\partial y}\right)\sp{m\sb y}\left({\partial\over\partial z}\right)\sp{m\sb z}x\sp{n\sb x}y\sp{n\sb y}z\sp{n\sb z}$$ is presented, and also a concise, quadrature-point-driven implementation of the standard Rys polynomial method for computing two-electron repulsion integrals. Finally, methods are presented for analytically differentiating self-consistent field and one-dimensional vibrational wavefunctions or energies to any order of any number of parameters. This is important for determining molecular response properties.Basis set effects through the level of 4f functions and correlation effects through the level of Brueckner orbital, double substitution coupled cluster theory are presented for CO. Vibrational transition energies accurate to better than 1% are obtained, and the dipole moment is in error by 0.07 Debye. Correlation is shown to have a small effect on the dipole polarizability and hyperpolarizability for large basis sets. The effects of local electric fields on the potential and properties of CO are examined. When perturbed by various local electrical environments, chemical shifts of carbon-13 and oxygen-17 are found to correlate in an essentially linear, but opposite, manner with the vibrational frequency. Electronic structure calculations show that the opposite change in chemical shifts is due to polarization of charge along the internuclear axis. This correlation is in accord with experimental data of a wide range of carbonmonoxyheme proteins, and so electrical perturbation is a possible cause of distal ligand effects.U of I OnlyETDs are only available to UIUC Users without author permissio