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Kinetic energy functionals: Exact ones from analytic model wave functions and approximate ones in orbital-free molecular dynamics

Abstract:

We consider the problem of constructing kinetic energy functionals in density functional theory. We first discuss the functional generated through the application of local–scaling transformations to the exact analytic wavefunctions for the Hookean model of 4He (a finite mass three–particle system), and contrast this result with a previous one for 1He (inffnite mass system). It is shown that an exact non–Born–Oppenheimer treatment not only leads to mass–correction terms in the kinetic energy, but to a basically different functional expression. In addition, we report and comment on some recently advanced approximate kinetic energy functionals generated in the context of the constraint–based approach to orbital–free molecular dynamics. The positivity and non–singularity of a new family of kinetic energy functionals specifically designed for orbital–free molecular dynamics is discussed. Finally, we present some conclusions.