First-Principles Study of Hydrogen Bonded Molecular
Conductor κ-H3(Cat-EDT-TTF/ST)2;
Electronic Structure and Role of the Hydrogen Bonds
Takao Tsumuraya
ICYS-Namiki
researcher
Proton dynamics in relatively short
intermolecular hydrogen bonds play an essential role in various functional
molecular materials such as organic ferroelectrics and biochemical reactions.
Recently, a new class of hydrogen bonded molecular conductors has been
synthesized; the compounds are based on catechol with ethylenedithiote-tetrathiafulvalene,
Cat-EDT-TTF and its diselena analog Cat-EDT-ST. Among
them, κ-type H3(Cat-EDT-TTF)2
is considered to be a dimer-type Mott insulator at ambient pressure and emerges
as a candidate of realizing quantum spin liquid down to lowest temperature [1].
In this crystal, two H(Cat-EDT-TTF) units share a
hydrogen (H) atom with relatively short O-H-O hydrogen bonds, and its
face-to-face dimers are formed in an anisotropic triangular lattice.
We study the electronic and structural
properties of κ-H3(Cat-EDT-TTF/ST)2
by first-principles density functional theory (DFT) calculations [2]. We report
unique properties of electronic structure compared with conventional molecular
conductors. To discuss a possibility of
spin-frustration, we evaluate inter-dimer transfer integrals by fitting the DFT
band structure. Regarding the hydrogen bonds, we calculate the potential energy
surface to investigate the degree of localization of the shared H atom and discuss
the stability of the structures. Lastly, we discuss how the positions of the
shared H atom influence to the electronic properties.
[1] T. Isono, H. Kamo, A. Ueda, K. Takahashi, M. Kimata,
H. Tajima, S. Tsuchiya, T. Terashima, S. Uji, and H. Mori, Phys. Rev. Lett. 112, 177201 (2014), and references therein.
[2]
T. Tsumuraya, H. Seo, R. Kato and T. Miyazaki, Phys. Rev. B 92, 035102 (2015).