It occurs naturally in ice caps on Earth, and is believed to be important in the outer Solar System on moons such as Titan and Triton which have a cold nitrogen atmosphere.
[1] The clathrate is much more resistant to shear stresses than pure water ice, yet the Young's modulus is about the same.
[1] At 0.6 °C a pressure of at least 171.3 bars is required to start forming nitrogen clathrate in water.
[3] Additional molecules can allow a mixed nitrogen clathrate to form at lower pressures.
The small pentagondodecahedral cavities have twelve pentagon shaped faces and a radius of 3.91 Å.
[1] At even higher pressures a phase called a filled ice structure (FIS) is formed.
[6] One quadruple point is at 143 bars and −1.3 °C where ice, clathrate hydrate, water and nitrogen gas are all present.
When the temperature is raised to 113K the amorphous phase changes to a crystalline form, and trapped nitrogen converts some ice into a clathrate.
A pressure of 77 bars is required to start forming clathrate from 17% carbon dioxide – 83% nitrogen mix at 0.6 °C.
Using tetrahydrofuran at 1 molar concentration allows a mixed THF-carbon dioxide-nitrogen clathrate to form at much lower pressures (3.45 bars), but much less gas is consumed and it is much slower.
[1] On the Saturnian moon Titan, nitrogen clathrate is predicted to be stable and exist along with ice on the surface, and deeper into the crust.
[12] In the gases coming out of comet 67P/Churyumov–Gerasimenko the ROSINA instrument on the Rosetta detected molecular nitrogen.