Molecular dynamics study of ice structural evolution

Molecular dynamics simulation is employed to study the structuralevolution of low density amorphous ice during its compression fromone atmosphere to 2.5,GPa. Calculated results show that highdensity amorphous ice is formed at an intermediate pressure of $sim$1.0,GPa; the O--O--O bond angle ranges from 83$^{circ}$ to113$^{circ}$, and the O--H$cdots$O bond is bent from 112$^{circ}$to 160$^{circ}$. Very high density amorphous ice is obtained byquenching to 80,K and decompressing the ice to ambient pressurefrom 160,K/1.3,GPa or 160,K/1.7,GPa; and the next-nearest O--Olength is found to be 0.310,nm, just 0.035,nm beyond the nearestO--O distance of 0.275,nm.