Compressed Ice Inter Electron-Pair Repulsion

Coulomb repulsion and mechanical disparity within the H-bond differentiate ice from other materials in response to compression. 

Compression shortens and strengthens the 0 H bond and meanwhile lengthens and softens H—O bond through repulsion toward 0 H and H-0 length 

Compression also stiffens the 0 H stretching phonons ( 400 cm ) and softens the H-0 stretching phonons ( 3,000 cm ). 

Cohesive energy loss of the H—O bond lowers the Tc for the VIII-VII phase transition, which derives the Ejj — 3.97 eV for ice. 

Entrapment of the bonding electrons and polarization of the lone electron pairs widen the bandgap. 

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