content_image/365534.jpg content_image/365535.jpg
## Appendix: The Classical atomistic model 

Here we briefly report the basic technical details of the force field for the tetrahedral molecules. Each molecule is characterized by N = 4 atoms of the same mass m$_{0}$ connected by anharmonic bonds. All atoms in the system interact according to a purely repulsive shifted 12-6 Lennard-Jones potential with a cutoff at 2 1 / $^{6}$σ : 

<img src='content_image/365534.jpg'>

r$_{iαjβ}$ defines the distance between the atom iα of the molecule α and the atom jβ of the molecule β . We define ε as a unit of energy. All atoms have the same excluded volume diameter σ , where σ is the unit of length. Neighboring atoms of a molecule are linked via an attractive FENE potential 

<img src='content_image/365535.jpg'>

R$_{0}$ = 1 . 5 σ is the divergence length and k = 30 ε/σ 2 the stiffness. 

## Acknowledgments 

We thank C.Peter, D.Donadio, M.Praprotnik and K.Kremer for discussions and for a critical reading of the manuscript; D.Manolopoulos for the path integral code and a critical reading of the manuscript. ABP acknowledge the financial support of the DAAD, LDS that of the MMM initiative of the Max-Planck Society. 

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