Core electrons Critical pressure

Skin supersolidity slipperizes ice. The H-O contraction, core electron entrapment and dual polarization yield the high-elasticity, self-lubrication, and low-friction of ice and the hydrophobicity of water surface as well, of which the mechanism is the same to that of metal nitride [45, 46] and oxide [47] surfaces. Nanoindentation measurements revealed that the elastic recovery coefficient of TiCrN, GaAlN, and a-Al203 surfaces could reach 100 % under a critical indentation load of friction (<1.0 mN) at which the lone pair breaks with a friction coefficient being the same order to ice (0.1) [42], see Fig. 39.2. Albeit the pressure and the nature of loading pin materials, both show the comparatively low friction coefficients. The involvement of lone pairs makes the nitride and oxide surfaces more elastic and slippery under the critical load. This understanding supplements mechanism for the slippery of ice surface and the hydrophobicity of ultrathin water films as well. 

The critical core mass required to reach all thermonuclear burning stages is called the Chandrasekhar mass. Its value is about 1.4 M0, but it depends on the mean molecular weight per free electron pe — reflecting the balance between pressure and gravity ... 

---