Chapter 17
Theoretical Analysis of Phase-Transition
Temperature of Hydrogen-Bonded Dielectric
Materials Induced by H/D Isotope Effect
Takayoshi Ishimoto and Masanori Tachikawa
Abstract We theoretically analyzed the H/D isotope effect for phase transition temperature (T c ) and geometrical changes of hydrogen-bonded dielectric materials by
using the multi-component molecular orbital method, which can take account the
quantum effect of proton, deuteron, triton, and muon. Taking into account the quantum effect of proton/deuteron using the MC_MO method directly, the difference of
T c , as well as, the geometry and electronic charge difference is universally elucidated. The origin of the isotope effect for hydrogen-bonded dielectric materials is
from the difference of the proton/deuteron wave distributions under the anharmonicity of the potential.
17.1 Introduction
The hydrogen-bonded dielectric material is classified into the (anti-) ferroelectric
materials having hydrogen bond in the crystal structure. Many hydrogen-bonded dielectric materials have been reported since the discovery of potassium dihydrogen
phosphate, KH 2 PO 4 (KDP), in 1935 [1]. The hydrogen-bonded dielectric materials have various hydrogen-bonded networks such as three-, two-, one-, and zerodimensional structures [2–5].
The phase transition of the hydrogen-bonded dielectric materials strongly depends on the nature of hydrogen-bonded networks. The hydrogen bond in the crystal
of hydrogen-bonded dielectric materials plays an important role to control various
physical properties. In particular, drastic change of the phase transition temperature
(T c ) of the hydrogen-bonded dielectric materials upon replacing hydrogen atoms
with deuterium is usually called the ‘isotope effect’. Sometimes the difference of
the T c between the hydrogen and deuterium compounds is more than 100 K. The
problem of its phase transition and the large isotope effect on such physical quantities as the T c has been one of the most interesting topics in this field. Although
there are many models and experimental results with respect to the isotope effect of
M. Tachikawa (B)
Quantum Chemistry Division, Graduate School of Science, Yokohama-City University, 22-2 Seto,
Kanazawa-ku, Yokohama 236-0027, Japan
e-mail: tachi@yokohama-cu.ac.jp
M. Hotokka et al. (eds.), Advances in Quantum Methods and Applications in
Chemistry, Physics, and Biology, Progress in Theoretical Chemistry and Physics 27,
DOI 10.1007/978-3-319-01529-3_17,
© Springer International Publishing Switzerland 2013
303
Theoretical Analysis of Phase-Transition
Temperature of Hydrogen-Bonded Dielectric
Materials Induced by H/D Isotope Effect
Takayoshi Ishimoto and Masanori Tachikawa
Abstract We theoretically analyzed the H/D isotope effect for phase transition temperature (T c ) and geometrical changes of hydrogen-bonded dielectric materials by
using the multi-component molecular orbital method, which can take account the
quantum effect of proton, deuteron, triton, and muon. Taking into account the quantum effect of proton/deuteron using the MC_MO method directly, the difference of
T c , as well as, the geometry and electronic charge difference is universally elucidated. The origin of the isotope effect for hydrogen-bonded dielectric materials is
from the difference of the proton/deuteron wave distributions under the anharmonicity of the potential.
17.1 Introduction
The hydrogen-bonded dielectric material is classified into the (anti-) ferroelectric
materials having hydrogen bond in the crystal structure. Many hydrogen-bonded dielectric materials have been reported since the discovery of potassium dihydrogen
phosphate, KH 2 PO 4 (KDP), in 1935 [1]. The hydrogen-bonded dielectric materials have various hydrogen-bonded networks such as three-, two-, one-, and zerodimensional structures [2–5].
The phase transition of the hydrogen-bonded dielectric materials strongly depends on the nature of hydrogen-bonded networks. The hydrogen bond in the crystal
of hydrogen-bonded dielectric materials plays an important role to control various
physical properties. In particular, drastic change of the phase transition temperature
(T c ) of the hydrogen-bonded dielectric materials upon replacing hydrogen atoms
with deuterium is usually called the ‘isotope effect’. Sometimes the difference of
the T c between the hydrogen and deuterium compounds is more than 100 K. The
problem of its phase transition and the large isotope effect on such physical quantities as the T c has been one of the most interesting topics in this field. Although
there are many models and experimental results with respect to the isotope effect of
M. Tachikawa (B)
Quantum Chemistry Division, Graduate School of Science, Yokohama-City University, 22-2 Seto,
Kanazawa-ku, Yokohama 236-0027, Japan
e-mail: tachi@yokohama-cu.ac.jp
M. Hotokka et al. (eds.), Advances in Quantum Methods and Applications in
Chemistry, Physics, and Biology, Progress in Theoretical Chemistry and Physics 27,
DOI 10.1007/978-3-319-01529-3_17,
© Springer International Publishing Switzerland 2013
303