Physical Properties of Gas Hydrates: A Review

Table 2

Comparison of properties of ice, sI, and sII hydrate crystal structures (data taken from [2, 3]).

Property	Ice ($I_h$)	Structure I	Structure II
Water molecules number	$4$	$46$	$136$
Lattice parameters at 273 K, nm	$a=0.452,\mathrm{\hspace{0.17em}\hspace{0.17em}}c=0.736$	$1.20$	$1.73$
Dielectric constant at 273 K	$94$	$~$58	$58$
Water diffusion correlation time, $\mu$s	$220$	$240$	$25$
Water diffusion activation energy, kJ/m	$58.1$	$50$	$50$
Isothermal Young’s modulus at 268 K, 10^9 Pa	$9.5$	$8.4\mathrm{\hspace{0.17em}\hspace{0.17em}}(\text{est}.)$	$8.2\mathrm{\hspace{0.17em}\hspace{0.17em}}(\text{est}.)$
Poisson’s ratio	$0.33$	$~$0.33	$~$0.33
Bulk modulus (272 K)	$8.8$	$5.6$	$NA$
Shear modulus (272 K)	$3.9$	$2.4$	$NA$
Compressional velocity ($V_p$), m/s	$3870.1$	$3778.0$	$3821.8$
Shear velocity ($V_s$), m/s	$1949$	$1963.6$	$2001.1$
Velocity ratio (comp./shear)	$1.99$	$1.92$	$1.91$
Linear thermal expn., at 200 K, ${\text{K}}^{-1}$	$56\hspace{0.17em}{10}^{-6}$	$77\hspace{0.17em}{10}^{-6}$	$52\hspace{0.17em}{10}^{-6}$
Adiab. bulk compress. (273 K), ${10}^{-11}$ Pa	$12$	$14\mathrm{\hspace{0.17em}\hspace{0.17em}}(\text{est}.)$	$14\mathrm{\hspace{0.17em}\hspace{0.17em}}(\text{est}.)$
Heat Capacity, J $\text{k}{\text{g}}^{-1}$ $\text{K}{-}^1$	$3800$	$3300$	$3600$
Thermal conductivity (263 K), W ${\text{m}}^{-1}$ ${\text{K}}^{-1}$	$2.23$	$0.49\pm 0.02$	$0.51\pm 0.02$
Refractive index, 638 nm, $-3^{°}$C	$1.3082$	$1.3460$	$1.350$
Density, kg ${\text{m}}^{-3}$	$916$	$912$	$940$