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A New Split Charge Equilibration Model and REPEAT Electrostatic Potential Fitted Charges for Periodic Frameworks with a Net Charge
journal contribution
posted on 2017-05-11, 00:00 authored by Mykhaylo Krykunov, Christopher Demone, Jason W.-H. Lo, Tom K. WooPeriodic frameworks that possess
a net charge, such as zeolites,
are an important class of materials in wide use. For guest–host
interactions to be simulated in these materials, partial atomic charges
are often used. In this work, we investigate two methods for the generation
of partial atomic charges in periodic systems having a net framework
charge. We first examine the validity of generating REPEAT electrostatic
potential fitted charges derived from periodic electronic structure
calculations, where a constant background charge is added to neutralize
the net charge on the framework. The constant background charge obviates
the need to add neutralizing counterions, which may induce artifacts
such as polarization in the infinite periodic system. The second method
we explore is the split charge equilibration (SQE) method for the
rapid generation of partial atomic charges. The original formulation
of the SQE method cannot be applied to systems with a net charge.
In this work, we reformulate the SQE method by transforming the split
charges into an atomic charge basis that allows for non-neutral systems
to be treated. The new SQE model, which we call SQEAB (for
atomic basis), was validated with a series of tests using both charged
and neutral metal organic frameworks and zeolites. It was shown that
SQEAB gives equivalent results to those of the original
SQE model for neutral systems. We then demonstrated that the SQEAB method is able to “capture” the chemical structure
of a charged framework better than that of the charge equilibration
model by comparing to REPEAT electrostatic potential fitted charges.