Chemical Physics Letters

Symmetry Adapted Perturbation Theory results for seven dimers considered in this work.

These are text files of all the data present in the figures of the paper.

Supporting Information about the manuscript

calculation method for experimental error

schematic representation of experimental technique

Starting coordinates in Angstrom for molecules I, IIA, IIB

The isobaric heat capacity and the coefficient of thermal expansion of a binary liquid mixture with a critical point of solution diverge as functions of temperature in the critical region. When the same liquids are used as solvents for chemical reactions, the van’t Hoff plot of the extent of reaction diverges in the critical region. According to the phase rule, the physical and chemical properties are isomorphic in the sense that in each case the critical behavior is determined by three fixed thermodynamic intensive variables. The predicted chemical effects are demonstrated by measuring the solubilities of lead salts, alone and together, in a mixture of isobutyric acid + water, which has a upper critical point of solution near 26 degrees C.

4-Aminopyridinium Perchlorate (APP), used to be known as a pyroelectric below 243K, is first discovered to be a new molecular ferroelectric in this work, which has a perfect electric hysteresis loops with a large spontaneous polarization of 1.0 mC/cm2 and a small coercive field of 0.67 kV/cm below 244.5 K. As shown in XRD,owing to the dramatic changes of the protonated cations and order-disorder of anions, the crystal symmetry of APP transforms from P21/c to P21 in this first-order phase transition, which is revealed by other measurements, such as differential scanning calorimetry, dielectric anomalies and Raman spectrum.Due to the lowing of the symmetry from the ideal tetrahedral geometry, splittings can be observed for the doubly degenerate modes. The modes of 405 cm-1 at 203 K were fitted by Gaussian functions.The symmetric stretching vibration at 405 cm-1 breaks up into two bands (402 cm-1, 408 cm-1) below transition temperature.

Fits of rotational spectra to give spectroscopic constants, as executed by using the program PGOPHER

All datas were performed on AFM