Quantum-chemical studies of quasi-one-dimensional electron systems. Part 2. Cumulenes and origin of the forbidden zone
This review is devoted to the basic problem in quantum theory of quasi-one-dimensional electron systems like polyenes (Part 1) and cumulenes (Part 2) - physical origin of the forbidden zone in these and analogous 1D electron systems due to two possible effects - Peierls instability (bond alternation) and Mott instability (electron correlation). Both possible contradiction and coexistence of the Mott and Peierls instabilities are summerized on the basis of the Kiev quantum chemistry team research projects.