Finding Molecular Structure in Molecular Wavefunctions

Molecular structure, one of the most central concepts of chemistry, has remained elusive from the perspective of all-particle quantum mechanics despite many efforts. Here, we propose a new definition of molecular structure applicable to arbitrary all-particle wavefunctions and implement a practical method based on Markov Chain Monte Carlo sampling and unsupervised machine learning. Application to the D3+ molecule shows unambiguously that it possesses an equilateral triangular structure. These results provide a major step forward in our understanding of molecular structure from fundamental physical principles.