Identification of normal modes responsible for ferroelectric properties in organic ferroelectric CBDC

Abstract

Structure and dynamics of hydrogen bonded organic ferroelectric CBDC (1-cyclobutene-1,2dicarboxylic acid, C 6 H 8 O 4 ) have been investigated using inelastic neutron scattering (INS) spectroscopy and first principles lattice dynamics. Vibrational modes of O-H-O bending, related with two different types of hydrogen bonds, inter and intra-molecular, are manifested as two sets of doublets in the range of 900-1400 cm −1 in the INS spectrum. First principles density functional theory (DFT) is used to assign these doublets to out-of-the-plane and in-plane vibrations of these two types of O-H-O bending modes. Correlating structure and dynamics we find that although the local structures of the hydrogen bonded protons are similar, their medium range order may influence their vibrational frequencies. Vibrational modes of non-hydrogen bonded protons also are assigned separately in the spectrum. Comparing the calculated and the experimental INS spectra it is predicted that hydrogen bonded O-H bonds are more anharmonic than non-hydrogen bonded C-H bonds. From the calculated Born effective charge tensor it is predicted that inter-molecular hydrogen bonds contribute more to the ferroelectric polarisation of CBDC than intra-molecular ones. A large LO-TO splitting of the O-H stretching mode at 2471 cm −1 is identified with the mode that has significant contribution to the ferroelectric polarisation. As this mode is sensitive to long range Coulomb interactions and is responsible for ferroelectric properties of the material, vibrational spectroscopy combined with DFT calculations is proposed as a characterisation tool to investigate ferroelectric properties in the CBDC molecular crystal.

Resolving the Chemical Formula of Nesquehonite via NMR Crystallography, DFT Computation, and Complementary Neutron Diffraction

“…The XRD measurement is seen to overestimate C−H bond lengths, and DFT with the GGA‐PBE functional consistently underestimates it. This result agrees with the findings of the previous study comparing the refinement of hydrogen positions by XRD and DFT computations [81,82] . The vdW‐DF improves the agreement and reduces the RMSE by 67 % compared to GGA‐PBE.…”

“…This result agrees with the findings of the previous study comparing the refinement of hydrogen positions by XRD and DFT computations. [81,82] The vdW-DF improves the agreement and reduces the RMSE by 67 % compared to GGA-PBE. These distances between H and C in the different refined structures are summarized in the Supporting Information, Table S1.…”

Lattice Dynamics in Organic Ferroelectrics Using Neutron Spectroscopy and Ab-Initio Modeling

“…This peak is denoted at C in Figure 2. These modes are observed in other hydrogen bonded ferroelectrics, such as croconic acid [8,11] and CBDC [12], around 1,000 − 1,100 cm −1 . The relative INS intensities of these modes are increasingly stronger from CBDC to PhMDA to croconic acid.…”

A Hybrid Model for Central Bank Digital Currency Based on Blockchain

“…Secondly, the solution for permissions in the alliance chain is using a method similar to build several subchains. It uses nodes with different permissions to maintain different blockchains with the same architecture [27]. The design does not fit the CDBC that needs to be unified.…”