Discipline: Chemistry and Chemical Sciences
Subcategory: Materials Science
Colomba M. Sanchez - California State University, San Bernardino
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, molecular or 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. In order 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, DIPA/two bromide system with only the center DIPA rotated, a DIPAB unit cell with one DIPA rotated, and a DIPAB unit cell with two DIPAs rotated. The transition from a relaxed state to the 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. Electron density plots of the systems show greater charge separation among the rotated intermediate states as opposed to the relaxed structures. In future work, the data from this study, modeling DIPAB and its clusters in its gaseous phase, will be compared to results for DIPAB from solid state calculations.
Funder Acknowledgement(s): National Science Foundation, 'CSUSB Center for Materials Science' NSF-HRD 1345163.
Faculty Advisor: Kimberley Cousins, KCousins@csusb.edu
Role: I calculated rotational energy barriers using Spartan 14' software, created the six systems using structures from Mercury's Cambridge Structural Database (CSD), and analyzed the results. My mentor guided me in situations where I was confused or headed in the wrong direction.