Abstract
sigma-Hole and lone-pair (lp)-hole interactions within sigma-hole center dot center dot center dot sigma-hole, sigma-hole center dot center dot center dot lphole, and lp-hole center dot center dot center dot lp-hole configurations were comparatively investigated on the pnicogen center dot center dot center dot pnicogen homodimers (PCl3)(2), for the first time, under field-free conditions and the influence of the external electric field (EEF). The electrostatic potential calculations emphasized the impressive versatility of the examined PCl3 monomers to participate in s-hole and lp-hole pnicogen interactions. Crucially, the sizes of s-hole and lp-hole were enlarged under the influence of the positively directed EEF and decreased in the case of reverse direction. Interestingly, the energetic quantities unveiled more favorability of the sigma-hole center dot center dot center dot lp-hole configuration of the pnicogen center dot center dot center dot pnicogen homodimers, with significant negative interaction energies, than sigma-hole center dot center dot center dot sigma-hole and lp-hole center dot center dot center dot lp-hole configurations. Quantum theory of atoms in molecules and noncovalent interaction index analyses were adopted to elucidate the nature and origin of the considered interactions, ensuring their closed shell nature and the occurrence of attractive forces within the studied homodimers. Symmetry-adapted perturbation theory-based energy decomposition analysis alluded to the dispersion force as the main physical component beyond the occurrence of the examined interactions. The obtained findings would be considered as a fundamental underpinning for forthcoming studies pertinent to chemistry, materials science, and crystal engineering.