Entanglement Entropy of Free Fermions with a Random Matrix as a One-Body Hamiltonian.

We consider a quantum system of large size and its subsystem of size , assuming that is much larger than , which can also be sufficiently large, i.e., 1≪L≲N.

Deductive molecular mechanics of four-coordinated carbon allotropes.

Deductive molecular mechanics is applied to study the relative stability and mechanical properties of carbon allotropes containing isolated σ-bonds. Our approach demonstrates numerical accuracy comparable to that of density-functional theory, but achieved with dramatically lower computational costs. We also show how the relative stability of carbon allotropes may be explained from a chemical perspective using the concept of strain of bonds (or rings) in close analogy to theoretical organic chemistry.