Size-dependent error of the density functional theory ionization potential in vacuum and solution
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 »
- Publication Date:
- Grant/Contract Number:
- SC0014437
- Type:
- 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)
- Research Org:
- Univ. of California, Merced, CA (United States)
- Sponsoring Org:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- 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
- OSTI Identifier:
- 1233558
- Alternate Identifier(s):
- OSTI ID: 1234092
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.,
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. doi: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.
doi: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},
journal = {Journal of Chemical Physics},
number = 24,
volume = 143,
place = {United States},
year = {2015},
month = {12}
}
- Free Publicly Accessible Full Text
- Accepted Manuscript (Publisher)
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Accepted Manuscript (DOE)
- Publisher's Version of Record
- https://doi.org/10.1063/1.4937417