Fictitious electronic degrees of freedom

For the second approach, called Car-Parrinello (CP) direct dynamics, the electronic wavefunction and nuclear motion are propagated simultaneously. When applying this method within the framework of density functional theory (DFT), the wavefunction is propagated by using fictitious electronic degrees of freedom with arbitrary masses. In ab initio and semiem-pirical electronic structure theories, the wavefunction is expanded in a set of basis functions and then as a superposition of zeroth-order electronic state... 

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