Quantum mechanics

Potential energy surface

Theorem of corresponding states

Atomic physics

Ab initio

Molecule

Reaction dynamics

Van der Waals radius

Physics

Mathematics

van der Waals force

Saddle point

Geometry

Excited state

Chemistry

Van der Waals surface

Van der Waals strain

Nature Communications

Encouraged by recent advances in revealing significant effects of van der Waals wells on reaction dynamics, many people assume that van der Waals wells are inevitable in chemical reactions. Here we find that the weak long-range forces cause van der Waals saddles in the prototypical C( 1 D )+D 2 complex-forming reaction that have very different dynamical effects from van der Waals wells at low collision energies. Accurate quantum dynamics calculations on our highly accurate ab initio potential energy surfaces with van der Waals saddles yield cross-sections in close agreement with crossed-beam experiments, whereas the same calculations on an earlier surface with van der Waals wells produce much smaller cross-sections at low energies. Further trajectory calculations reveal that the van der Waals saddle leads to a torsion then sideways insertion reaction mechanism, whereas the well suppresses reactivity. Quantum diffraction oscillations and sharp resonances are also predicted based on our ground- and excited-state potential energy surfaces.

Dynamical importance of van der Waals saddle and excited potential surface in C(1D)+D2 complex-forming reaction