Local and semilocal density functional computations for crystals of 1-alkyl-3-methyl-imidazolium salts

Mario Del Popolo, C. Pinilla, Pietro Ballone

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

The accuracy and reliability of popular density functional approximations for the compounds giving origin to room temperature ionic liquids have been assessed by computing the T=0 K crystal structure of several 1-alkyl-3-methyl-imidazolium salts. Two prototypical exchange-correlation approximations have been considered, i.e., the local density approximation (LDA) and one gradient corrected scheme [PBE-GGA, Phys. Rev. Lett. 77, 3865 (1996)]. Comparison with low-temperature x-ray diffraction data shows that the equilibrium volume predicted by either approximations is affected by large errors, nearly equal in magnitude (~10%), and of opposite sign. In both cases the error can be traced to a poor description of the intermolecular interactions, while the intramolecular structure is fairly well reproduced by LDA and PBE-GGA. The PBE-GGA optimization of atomic positions within the experimental unit cell provides results in good agreement with the x-ray structure. The correct system volume can also be restored by supplementing PBE-GGA with empirical dispersion terms reproducing the r-6 attractive tail of the van der Waals interactions.
Original languageEnglish
Article number144705
Pages (from-to)144705-1-144705-11
Number of pages11
JournalJournal of Chemical Physics
Volume126
Issue number14
DOIs
Publication statusPublished - Apr 2007

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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