Range-Separation Parameter in Tuned Exchange–Correlation Functionals: Successive Ionizations and the Fukui Function

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe range-separation parameter in tuned, range-separated exchange-correlation functionals is investigated in two contexts. First, the system-dependence of the parameter is investigated for a series of systems obtained by successively ionising a single species, paying particular attention to the degree of linearity in the energy versus electron number curve. The parameter exhibits significant system-dependence and so achieving near-linearity in one segment of the curve leads to strong non-linearity in other segments. This provides a challenging test case for the development of new functionals designed to overcome the known problems of this class of functional. Next, the study considers whether a range-separation parameter tuned to a Koopmans energy condition is also applicable for the analogous density condition. This is tested by comparing two formulations of the Fukui function of conceptual density functional theory, * To whom correspondence should be addressed † Durham University ‡ Vrije Universiteit Brussel 1 for three representative systems. Both formulations yield the same general features and are not highly sensitive to the range-separation parameter. However, the agreement between the two is near-optimal when the energy-tuned parameter is used, indicating that this parameter is applicable for the analogous density condition.

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