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Title: Size-dependent error of the density functional theory ionization potential in vacuum and solution

Abstract

Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute amore » fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. As a result, in vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.« less

Authors:
 [1];  [1]
  1. Univ. of California, Merced, CA (United States)
Publication Date:
Research Org.:
Univ. of California, Merced, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1233558
Alternate Identifier(s):
OSTI ID: 1234092
Grant/Contract Number:  
SC0014437
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 143; Journal Issue: 24; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; density functional theory; solvents; ionization; exact exchange; size-dependent error; polarization; single molecule techniques

Citation Formats

Sosa Vazquez, Xochitl A., and Isborn, Christine M. Size-dependent error of the density functional theory ionization potential in vacuum and solution. United States: N. p., 2015. Web. doi:10.1063/1.4937417.
Sosa Vazquez, Xochitl A., & Isborn, Christine M. Size-dependent error of the density functional theory ionization potential in vacuum and solution. United States. https://doi.org/10.1063/1.4937417
Sosa Vazquez, Xochitl A., and Isborn, Christine M. 2015. "Size-dependent error of the density functional theory ionization potential in vacuum and solution". United States. https://doi.org/10.1063/1.4937417. https://www.osti.gov/servlets/purl/1233558.
@article{osti_1233558,
title = {Size-dependent error of the density functional theory ionization potential in vacuum and solution},
author = {Sosa Vazquez, Xochitl A. and Isborn, Christine M.},
abstractNote = {Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. As a result, in vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.},
doi = {10.1063/1.4937417},
url = {https://www.osti.gov/biblio/1233558}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 24,
volume = 143,
place = {United States},
year = {Tue Dec 22 00:00:00 EST 2015},
month = {Tue Dec 22 00:00:00 EST 2015}
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 24 works
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Figures / Tables:

FIG. 1 FIG. 1: Change in DFT computed ionization potential (IP) compared to a single molecule for increasing number of noninteracting methane, ethene, and benzene molecules in vacuum.

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Works referencing / citing this record:

Dielectric Screening Meets Optimally Tuned Density Functionals
journal, April 2018


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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.