Optimizing the geometry of stereoregular polymers. III. Polyyne and the basis set quasi-linear dependence

The ground-state geometry of polyyne is determined ab initio by crystal-orbital calculations taking into account the long-range effects up to the third-order correction. The basis set quasi-linear dependence problem is addressed in detail and the impact of removing some dimensions of the atomic basis set on the geometrical derivatives of the total energy is quantitatively evaluated. Comparisons with other theoretical works using either crystal-orbital or molecular orbital procedures are carried out.