Electronic structure and related properties of the ferroelectric crystal triglycine sulfate

The electronic band structure and related physical properties of the crystal triglycine sulfate (TGS), (NH2CH2COOH)(3) center dot H2SO4, in the ferroelectric phase P2(1) have been calculated using the first principles Linear Combination of Atomic Orbitals (LCAO) code CRYSTAL'06 at the B3LYP level of theory. The interactions between the quasi-separate three glycine groups and the sulfate complex have been studied by the analysis of the density of states of the crystal. The glycine 2 group was found to be the zwitterion in the optimized structure. Ten coefficients of the elastic stiffness tensor C-kl, four coefficients of the tensor of the elastoelectrical effect e(ki), and the spontaneous polarization P-s of TGS have been calculated for the first time and have been found to agree well with experimental data. Extrema are found in the elastoelectric coefficient e(22) as a function of the strain epsilon(2), and in the spontaneous polarization P-s as a function of the unit cell volume. (C) 2008 Elsevier Ltd. All rights reserved.