Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

Table 1 Layer spacing and molar potential energy of water (MC simulation)¹⁵ and self-diffusion coefficients for interlayer water (MD simulation) in Cs-smectite hydrates

Hydrate	MC steps ^a	Layer spacing/Å	Potential energy of water/kJ mol^{-1 b}	Self-diffusion coefficient, D_w/10^-9 m² s^-1 ^c
1/3 water monolayer
Cs-hectorite	10⁶	12.37 ± 0.08	-47.43 ± 3.53	0.229 ± 0.001
Cs-beidellite^d	4 × 10⁶	12.31 ± 0.10	-42.98 ± 4.58	0.342 ± 0.002
Cs-montmorillonite	10⁶	12.46 ± 0.09	-32.33 ± 4.04	Nonlinear^e
2/3 water monolayer
Cs-hectorite	3.0 × 10⁶	12.41 ± 0.07	-46.56 ± 2.00	0.685 ± 0.006
Cs-montmorillonite	3.5 × 10⁶	12.68 ± 0.10	-36.66 ± 2.12	1.168 ± 0.006
Bulk liquid water^f			-35.4 ± 0.2³¹	2.3³²

^aMonte Carlo steps required for convergence. ^b(Total potential energy of hydrate – total potential energy of clay mineral) ÷ moles of water per simulation cell.¹³ ^cValue calculated from linear regression of the mean-square displacement (MSD) on elapsed time with P = 0.05 confidence interval.¹⁵ ^dThis hydrate exhibited MC convergence only at the lower water content.¹⁵ ^eThis hydrate did not produce a linear relationship between MSD and elapsed time.¹⁵ ^fMCY water³³ yields D_w = 2 × 10^-9 m² s^-1.

ISSN: 1467-4866