Ice crystal structure parametric model

October 2017

Ismo T.S. Heikkinen
Aalto University
ELEC-L3999 3D Printing of Open Source Hardware for Science

Licensed under Creative Commons Attributions CC BY.

Details about the model:

Use the OpenSCAD script to modify the parametric model to suit your needs.

Water molecules (H2O) consist of one oxygen (O) and two hydrogen (H), which are bound together by the covalent bond. The angle between the hydrogen atoms is approximately 107 degrees [1], and the atomic radii of oxygen and hydrogen are 0.6 Å and 0.25 Å, respectively [2].

H2O molecules are bonded to each other by the hydrogen bond. Each O atom can accept two H bonds, and each H atom donates one H bond. In normal conditions H2O molecules are packed in a hexagonal wurtzite lattice, but in Pauling's model there is no long-range order in the H2O molecule or H bond orientations [1].

In the water molecule the distance between H and O atoms is roughly 0.96 Å, but in this model it is approximated that the H atoms are located on the surface of the O atom. The bond length between the H2O molecules is approximately 7.82 Å (13 times the atomic radius of oxygen) [1].

The model scales in relation to the radius of the oxygen atom: if the radius of the O atom is 7 mm, the radius of the H atom is 2.92 mm. With the same scale the intermolecular distance is 9.1 cm. All distances in the source file are in 5E-12 m.

This model is applicable to all three-atom molecules (angle between atoms and atom sizes just need to adjusted accordingly).

References:
[1] Physics of Ice, V.F. Petrenko and R.W. Whitworth, OUP Oxford, 1999 (2003)
[2] Wikipedia, Atomic radii of the elements (data page), https://en.wikipedia.org/wiki/Atomic_radii_of_the_elements_(data_page)