Local temperature changes in molecular interactions

The local temperature in quantum mechanics is a non-univocal quantity; however, one can select a proper kinetic energy to compute it and obtain a physically consistent behavior. Herein, we study the local temperature and local temperature differences in atoms, molecules, and chemical interactions in a topographic fashion. Our results indicate that atomic temperatures can be defined at a given cut-off distance while maintaining qualitative periodicity. When two atoms in a molecule experience a bonding interaction, there exists a temperature decrease between the interacting species. This endows stability to the system by lowering the kinetic energy. Our findings also suggest that when two chemical species are weakly bonded, an isosurface reflects a temperature decrease and might serve as a criterion to identify and characterize weak interactions from a thermodynamic viewpoint.