Abstract: | Cadmium mercury thiocyanate (CdHg(SCN)4, CMTC) and its two lewis base adducts: cadmium mercury thiocyanate dimethyl‐sulphoxide (CdHg(SCN)4(H6C2OS)2, CMTD) and cadmium mercury thiocyanate glycol monomethyl ether (CdHg(SCN)4(C3H8O2), CMTG) have been discovered as nonlinear optical (NLO) crystal materials. Their structural, optical and physicochemical properties were characterized by X‐ray powder diffraction (XRPD), infrared spectroscopy, vis/UV/NIR spectra and thermal analysis. It is discovered that their transparency cutoffs lie in the UV region and CMTD crystals possess the shortest cutoff wavelength among the three crystal materials. |