Figure 2. Pyroelectricity and crystal structure of α-glycine doped with L-amino acids.

First row (a–c): measured pyroelectric signal of the doped crystals at 25 °C. Second row (d–f): experimental temperature dependence of the pyroelectric coefficient. Error bars represent s.e.m. values. The pyroelectric effect is fully reversible with temperature and does not decay with time (>10 months), which implies that once occluded, the dopant molecules do not diffuse from L and L′ to the D or D′ sites of the crystal. Third row (g–i): DFT computed most stable conformation for each system, along with a three-dimensional intensity map depicting molecular distortion in the unit cell, with the colours representing the dopant-induced distortion angle of the nitrogen to carboxylic carbon vector, relative to its orientation in the undoped glycine crystal (note the different scale for each system). Fourth row (j–l): MD-computed temperature-dependent polarization for each system. The dots are average values and the error bars represent the s.d.