Direct quantum chemistry
Encyclopedia
Direct quantum chemistry covers a set of quantum chemical
methods not using the Born–Oppenheimer representation. Direct quantum chemistry considers the motion of the nuclei and the electrons on the same time scales. The method therefore considers the molecular Hamiltonian
as a whole without trying to solve separately the Schrödinger equation
associated to the electronic molecular Hamiltonian. Though the method is non-adiabatic it is distinguishable from most non adiabatic methods for treating the molecular dynamics, which typically use the Born-Oppenheimer representation, but become non-adiabatic by considering vibronic coupling
explicitly.
Direct quantum chemistry is applied in the modelling of high-speed atomic collisions, where the nuclear motion may be comparable or faster than the electronic motion.
The group of Yngve Öhrn in Gainesville, Florida
has been a pioneer in this field. He applied the method to the collision between two hydrogen atom
s.
Quantum chemistry
Quantum chemistry is a branch of chemistry whose primary focus is the application of quantum mechanics in physical models and experiments of chemical systems...
methods not using the Born–Oppenheimer representation. Direct quantum chemistry considers the motion of the nuclei and the electrons on the same time scales. The method therefore considers the molecular Hamiltonian
Molecular Hamiltonian
In atomic, molecular, and optical physics as well as in quantum chemistry, molecular Hamiltonian is the name given to the Hamiltonian representing the energy of the electrons and nuclei in a molecule...
as a whole without trying to solve separately the Schrödinger equation
Schrödinger equation
The Schrödinger equation was formulated in 1926 by Austrian physicist Erwin Schrödinger. Used in physics , it is an equation that describes how the quantum state of a physical system changes in time....
associated to the electronic molecular Hamiltonian. Though the method is non-adiabatic it is distinguishable from most non adiabatic methods for treating the molecular dynamics, which typically use the Born-Oppenheimer representation, but become non-adiabatic by considering vibronic coupling
Vibronic coupling
In theoretical chemistry, the vibronic coupling terms, , are proportional to the interaction between electronic and nuclear motions of molecules. The term "vibronic" originates from the concatenation of the terms "vibrational" and "electronic"...
explicitly.
Direct quantum chemistry is applied in the modelling of high-speed atomic collisions, where the nuclear motion may be comparable or faster than the electronic motion.
The group of Yngve Öhrn in Gainesville, Florida
Gainesville, Florida
Gainesville is the largest city in, and the county seat of, Alachua County, Florida, United States as well as the principal city of the Gainesville, Florida Metropolitan Statistical Area . The preliminary 2010 Census population count for Gainesville is 124,354. Gainesville is home to the sixth...
has been a pioneer in this field. He applied the method to the collision between two hydrogen atom
Hydrogen atom
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively-charged proton and a single negatively-charged electron bound to the nucleus by the Coulomb force...
s.