“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27] Recently, these calculations have greatly improved the understanding of the origin of crystal mechanics and piezoelectricity for several piezoelectrics, such as (R-/S-(N-methylbenzylaminium))PbBr 3 , (Hmdabco)(NH 4 )X 3 (Hmdabco 2+ = 1-methyl-1,4-diazabicyclo-[2.2.2]octane-1,4-diium, X = Cl, Br, or I), and (benzyltrimethylammonium) 2 CoBr 4 . 19,20,25,26 Moreover, with the advantage of lower manufacturing costs when compared with conventional inorganic piezoelectric crystals, several molecule-based piezoelectric crystals have been assembled into piezoelectric generation devices for harvesting environmental vibrational energy to meet the requirements for self-energy supply in low-power devices. 11,12,22,23,26,[28][29][30][31][32][33][34][35][36][37][38] It was found that ferroelectrics, belonging to a class of piezoelectrics in which the direction of spontaneous polarization can be reversed by an applied electric field 13 and following a ferroelectric group-subgroup relationship during phase transitions, 39,40 generally have a higher piezoelectric effect than non-ferroelectric ones, and are thus more desired in seeking advanced piezoelectric materials.…”