“…Compared with centrosymmetric solids, acentric solids draw growing attention from the research community due to the chance of studying directional physical properties such as second harmonic generation, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] nonreciprocal responses, [16][17][18][19][20][21] etc. From a chemistry perspective, various strategies have proved efficient to influence the creation of a noncentrosymmetric (NCS) structure, including incorporating second order Jahn-Teller distortion 22,23 and conjugated structure motifs such as distorted FeS 4 14, 24 or GeS 4 tetrahedra, 25,26 WO 5 , 27 LaO 6 Br 3 , 28 etc. Another systematic way to influence a NCS structure is through incorporating atoms with stereochemically active lone pairs (SCALPs), including Tl + , Sn 2+ , Pb 2+ , As 3+ , Sb 3+ , Bi 3+ , Te 4+ , etc., with many successful examples such as Tl + in Tl 4 (OH) 2 CO 3 29 and TlXF 3 (X = Be, Sr); 30 Sn 2+ in Sn 2 P 2 S 6 , [31][32][33] Sn 2 PO 4 X (X = F, Cl), 34 and Sn[B 2 O 3 F 2 ]; 35 Pb 2+ in Pb 2 P 2 S 6 , 36 Pb 3 P 2 S 8 , 15 Pb 13 O 6 Cl 4 Br 10 , 37 Pb 13 O 6 Cl 7 Br 7 , 37 and Pb 13 O 6 Cl 9 Br 5 ; 37 As 3+ in K 3 AsS 4 , 38 Li...…”