Approximately diabatic states from block diagonalization of the electronic Hamiltonian

Autor:	T. Pacher, Horst Köppel, Lorenz S. Cederbaum
Rok vydání:	1988
Předmět:	Hamiltonian mechanics Physics Nuclear motion Jahn–Teller effect Diabatic General Physics and Astronomy Electronic structure Unitary transformation Electronic states symbols.namesake Theoretical physics Quantum mechanics symbols Physical and Theoretical Chemistry Hamiltonian (quantum mechanics)
Zdroj:	The Journal of Chemical Physics. 89:7367-7381
ISSN:	1089-7690 0021-9606
Popis:	In many cases of interest there is only a small number of electronic states which interact with each other through the nuclear motion and are well‐separated energetically from the other states. The aim of this work is to find a nearly diabatic (quasidiabatic) representation for the coupled states in which their coupling becomes small. Block diagonalization of the electronic Hamiltonian can accomplish this goal. It is achieved by a unitary transformation T which is uniquely determined by a ‘‘least action principle’’ which demands that T ‘‘does not do anything but block diagonalization.’’ By the help of the transformation we arrive at a decoupling of the relevant states from the rest and have to deal with a small matrix Hamiltonian. We have investigated in detail this block diagonalization procedure and succeeded in calculating the matrix elements of the total Hamiltonian in the new basis in closed form, in a nonperturbative way. Qualitative criteria are given to decide in which cases the method can success...
Databáze:	OpenAIRE
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