Table I

Table I
Crystallographic Information of Common Molybdenum Carbide Phases
Phase		Type	Range of temperature, stability	Structure	Lattice parameter, Å (ICSD)^a	Space group (ICSD)^a	C atom position	Stacking sequence
β-Mo2C^b hcp	α-Mo2C	ζ-Fe2N	Room temperature (76, 80, 81)	Orthorhombic (distorted) hcp	a = 4.724	Pbcn (60)	Octahedral	ABAB
					b = 6.004
					c = 5.199
	ɛ-Mo2C	ɛ-Fe2N	Intermediate temperature (81, 92)	Hexagonal/trigonal hcp	a = 5.190	P-31m (162)	Octahedral	ABAB
					b = 5.190
					c = 4.724
	β-Mo2C	Nb2N/W2C	High temperatures^d (76, 80, 81, 93)	Hexagonal (filled) hcp	a = 3.002	P63/mmc (194)	Octahedral	ABAB
					b = 3.002
					c = 4.724
η-MoC		η-Mo3C2	Metastable (84, 94, 95) Stable T > 1700°C (71)	Hexagonal (complex) hcp	a = 3.010	P63/mmc (194)	Octahedral	ABCACB
					b = 3.010
					c = 14.610
α-MoC1-x^b fcc	δ-MoC^c	NaCl	Metastable (84) Stable T > 1700°C (71)	Cubic fcc	a = 4.270	Fm-3m (225)	Octahedral	ABCABC
					b = 4.270
					c = 4.270
γ-MoC		WC type	Room temperature (84, 93, 96)	Hexagonal simple	a = 2.903	P-6m2 (187)	Trigonal prismatic	AAAA
					b = 2.903
					c = 2.828
γ’-MoC		TiAs/TiP	Always metastable^e (84, 93, 95)	Hexagonal	a = 2.932	P63/mmc (194)	Trigonal prismatic/octahedral	AABB
					b = 2.932
					c = 10.97
^aInorganic Crystal Structure Database ^bNames commonly found in catalytic and experimental studies ^cAlso referred to as α-MoC, δ is mainly found in computational studies ^dNormally referred to as the L’3 disordered phase ^eIntermediate between β and γ during carburisation with carbon monoxide (can be considered as an oxycarbide)

^aInorganic Crystal Structure Database

^bNames commonly found in catalytic and experimental studies

^cAlso referred to as α-MoC, δ is mainly found in computational studies

^dNormally referred to as the L’3 disordered phase

^eIntermediate between β and γ during carburisation with carbon monoxide (can be considered as an oxycarbide)