A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

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Volume 542 (June 2012)

A&A, 542 (2012) A82

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Table 3

Parameters for clathrate formation/dissociation.

Symbol	Name	Unity	Value

n _hyd	Hydrate number		6^α
	Bulk density of water structure of clathrate	kg m^-3	790
k^cl	Heat conductivity of clathrate	W m^-1 K^-1
	Valid temperature range for values
	T ≤ 80 K		5.47954 × 10^-2 T − 3.13102 × 10^-3 T²
			+ 9.40412 × 10^-5 T³ − 1.29299 × 10^-6T⁴
			+ 6.38159 × 10^-9T⁵^β
	T ≥ 80 K		2.1 × 10^-4 T + 0.43^χ
H	Absolute enthalpy of dissociation of guest trapped in clathrate	J mol^-1
	CO		15 720^δ
	CO₂		21 327^δ
	CH₄		18 130^ε
	H₂S		25 404^δ
	Nominal kinetics constant of formation of clathrate	mol m^-2 Pa^-1 s^-1	3 × 10^-13^φ
	Nominal kinetics constant of dissociation of clathrate	mol m^-2 Pa^-1 s^-1	^φ

Notes.

^α

Sloan (1998); Sun & Mohanty (2006);

^β

data fit of Krivchikov et al. (2005a,b, 2008);

^χ

Krivchikov et al. (2005a,b);

^δ

provided by the Clausius-Clapeyron equation from data given by references in Table 2;

^ε

Handa (1986b);

^φ

Englezos et al. (1987); Schmitt (1986).

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