Polar distortions in hydrogen bonded organic ferroelectrics

Although ferroelectric compounds containing hydrogen bonds were among the first to be discovered, organic ferroelectrics are relatively rare. The discovery of high polarization at room temperature in croconic acid [Nature \textbf{463}, 789 (2010)] has led to a renewed interest in organic ferroelectrics. We present an ab-initio study of two ferroelectric organic molecular crystals, 1-cyclobutene-1,2-dicarboxylic acid (CBDC) and 2-phenylmalondialdehyde (PhMDA). By using a distortion-mode analysis we shed light on the microscopic mechanisms contributing to the polarization, which we find to be as large as 14.3 and 7.0\,$\mu$C/cm$^{2}$ for CBDC and PhMDA respectively. These results suggest that it may be fruitful to search among known but poorly characterized organic compounds for organic ferroelectrics with enhanced polar properties suitable for device applications.Comment: Submitte

Isolated Adrenocorticotropin Deficiency Associated with Delirium and Takotsubo Cardiomyopathy

We report a 65-year-old woman with isolated adrenocorticotropic hormone (ACTH) deficiency. The patient was transported to the emergency outpatient department by ambulance complaining of malaise and nausea. Because her laboratory data revealed hyponatremia, we performed endocrinological examinations and diagnosed isolated ACTH deficiency. After admission, she went into a delirious state and suffered from takotsubo cardiomyopathy due to adrenal insufficiency. Replacement therapy with hydrocortisone sufficiently improved her delirium and cardiomyopathy. We conclude that her unstable mental state and myocardial dysfunction were closely related to adrenal insufficiency and suggest that adrenal crisis may cause delirium and Takotsubo cardiomyopathy

BEDO-TTFの有機電荷移動錯体における強く安定化された金属状態の性質及びその起源に関する研究

本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである京都大学0048新制・課程博士博士(理学)甲第6689号理博第1824号新制||理||994(附属図書館)UT51-97-H73京都大学大学院理学研究科化学専攻(主査)教授 斎藤 軍治, 助教授 吉村 一良, 助教授 矢持 秀起学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

A straightforward method using the sign of the piezoelectric coefficient to identify the ferroelectric switching mechanism

Abstract Some organic ferroelectrics have two possible switching modes: molecular reorientation and proton transfer. Typical examples include 2,5-dihydroxybenzoic acid (DHBA) and Hdabco-ReO $$_4$$ 4 (dabco = diazabicyclo[2.2.2]octane). The direction and amplitude of the expected polarization depends on the switching mode. Herein a straightforward method to identify the ferroelectric switching mechanism is demonstrated. First, the relationship between the polarization vectors corresponding to the two modes is illustrated using the Berry phase. Second, the theoretical background for the sign of the piezoelectric coefficient is used to decide which mode occurs. Finally, comparing the theoretically calculated piezoelectric coefficients to the experimental results confirms the switching mode of each compound

Quantum Phenomena Emerging Near a Ferroelectric Critical Point in a Donor–Acceptor Organic Charge-Transfer Complex

When a second-order transition point is decreased to zero temperature, a continuous quantum phase transition between different ground states is realized at a quantum critical point (QCP). A recently synthesized organic charge-transfer complex, TTF-2,5-QBr 2 I 2 , provides a platform for the exploration of the quantum phenomena that accompany a ferroelectric QCP. Here, we summarize the recent results showing the quantum phenomena associated with the ferroelectric QCP in TTF-2,5-QBr 2 I 2 . Whereas the enhanced quantum fluctuations lead to quantitative changes in the critical exponents of the critical phenomena, they qualitatively change the nature of the domain-wall kinetics from thermally activated motion to temperature-independent tunneling motion. The present findings highlight the great influence of quantum fluctuations on the low-temperature physical properties and suggest that TTF-2,5-QBr 2 I 2 is a model system for the uniaxial ferroelectric QCP

High-Temperature and Pressure-Induced Ferroelectricity in Hydrogen-Bonded Supramolecular Crystals of Anilic Acids and 2,3-Di(2-pyridinyl)pyrazine

Cocrystallization of anilic acids (H₂xa) and 2,3-di­(2-pyridinyl)­pyrazine (dppz) affords a variety of molecular geometries, including hydrogen-bonding and supramolecular structures. Proton-transferred 1:1 salts of [H-dppz]­[Hca] and [H-dppz]­[Hba] (H₂ca = chloranilic acid, H₂ba = bromanilic acid) were found to host room-temperature ferroelectricity with a spontaneous polarization of 3–4 μC/cm² along the hydrogen-bonded chains. Compared with the Curie points of other supramolecular ferroelectrics, those of the salts are relatively high (402 K and >420 K, respectively) because of the elongated hydrogen bonds, which stabilize the proton-ordered state against thermal agitation. In addition to the ferroelectric black (α) form, dppz and H₂ba gave two different crystal forms with a 2:3 ratio: the brown β form of [H_1.5-dppz]₂[Hba]₃ and the brownish-red γ form of [H-dppz]₂[Hba]₂[H₂ba]. Mixed solutions of dppz with the less acidic fluoranilic acid (H₂fa) exhibit valence instability; the H₂fa molecules remain mostly neutral in absolute ethanol, whereas methanol (MeOH) solution apparently increases the deprotonated Hfa^– content. Crystallizations of these solutions gave a neutral [dppz]­[H₂fa] cocrystal and ionic [H-dppz⁺]­[Hfa^–]·MeOH salt, respectively. The ferroelectricity induced by a modest hydrostatic pressure corroborates the conclusion that the ionic state with a dipolar [H-dppz⁺]­[Hfa^–] chain is energetically close to the nonpolar neutral ground state of the [dppz]­[H₂fa] crystal