Subset System Study Of Diisopropylammonium Bromide: An Organic Ferroelectric Crystal

RM 215

Diisopropylammonium bromide (DIPAB) is an organic molecular ferroelectric crystal that switches its polarity through an applied electric field. DIPAB has a large ferroelectric response of 23 μC/cm2, which is comparable to commercially used inorganic ferroelectrics, such as barium titanate (BTO). DIPAB is an alternative to toxic inorganic ferroelectrics because of its environmentally friendly quality. Ferroelectrics have commercial uses such as data storage, flexible electronics, ferroelectric thin-film memories, actuation and electro-optics. This research used Spartan ’14 software to calculate the rotational barrier of the molecule during the transition from a relaxed state to a hypothetical intermediate symmetrical state as it switches its polarity. A basis set study was performed using Hartree-Fock (HF) and Density-Functional theory (DFT) B3LYP functionals which showed that HF 6-31G* and DFT B3LYP 6-311G* produced reliable results with a reasonable resource allocation. To understand what occurs during the polarization switch, vacuum calculations were performed on structures extracted from the Cambridge Structural Database (CSD) as six different types of systems: DIPA cation system, single DIPAB system, DIPA dibromide system, three DIPA/two bromide system with center DIPA rotated, one DIPAB rotated in unit cell, and both DIPAB rotated in unit cell. The transition from a relaxed state to intermediate state represents a possible transition mode that occurs as DIPAB changes from one polar state to another. A correlation between the size of the system and its rotational barrier shows that as the system size increased, the rotational energy barrier increased.