Table 1.

Summary of typical MMCs crystal structure parameters and their properties

MMCs	Space group	Crystal structures	Lattice parameters [Å]	Distance d a) [nm]	References
SiS		Orthorhombic	a = 4.61; b = 3.27	0.228–0.234	[ 62 , 63 ]
SiSe		Orthorhombic	b = 5.0; b = 3.54	0.246–0.249	[ 63 , 64 ]
GeS	${\mathrm{D}}_{2\mathrm{h}}^{16}$	Orthorhombic	a = 4.3; b = 10.47; c = 3.65	0.56	[ 65 , 66 , 67 ]
GeSe	${\mathrm{D}}_{2\mathrm{h}}^{16}$	Orthorhombic	a = 10.84; b = 3.83; c = 4.39	–	[ 67 , 68 , 69 ]
SnS	${\mathrm{D}}_{2\mathrm{h}}^{16}$	Orthorhombic	a = 4.33; b = 11.19; c = 3.98	0.56	[ 70 ]
SnSe	${\mathrm{D}}_{2\mathrm{h}}^{16}$	Orthorhombic	a = 11.49; b = 4.15; c = 4.44	0.62	[ 71 , 72 ]

^a)Distance d is thickness of a monolayer MXs.