Table 5. Mulliken Bond Population for the Atom Pairs between Adsorbed Molecules (CH₄, CO₂) and Neighboring Surface Ions (Ca²⁺, CO₃^2–)^a.

absorption systems	atom pairs	overlap population	interatomic length (Å)
CH4 on calcite(10.4)	H1–O32	–0.01	2.9149
	H2–O47	0.00	2.9543
CH4 on aragonite(011)Ca	H1–O32	–0.01	2.9112
	H1–O36	0.00	2.8975
	H2–O8	0.00	2.8950
	H2–O18	–0.01	2.8372
	H3–O32	–0.01	2.8784
CH4 on vaterite(010)CO3	H1–O20	–0.01	2.5088
	H1–O44	–0.01	2.9252
	H2–O8	–0.01	2.7314
CO2 on calcite(10.4)	O50–Ca1	0.05	2.6361
	C17–O47	0.01	2.7357
CO2 on aragonite(011)Ca	O50–Ca2	0.06	2.5128
CO2 on vaterite(010)CO3	O49–Ca10	0.03	2.7892
	O50–Ca6	0.03	2.8444
	C17–O8	0.01	2.6498
	C17–O44	0.00	2.6256

^aThe atom no. is shown in Figure 4.