How to calculate theoretical density

The maximum achievable #density of a particular element, compound, or alloy, assuming no internal voids or contaminants. It is calculated from the number of atoms per unit cell and the measurement of the lattice parameters.
To calculate a #theoretical #density, multiply the number of atoms per unit cell by the atomic weight, then divide by the result of the product of the volume per unit cell multiplied by #Avogadro's number.

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   • The structure of crystalline solids part 1...  

Some of the #properties of #crystalline solids depend on the crystal structure of the material, the manner in which atoms, ions, or molecules are spatially arranged.
There is an extremely large number of different crystal structures all having long-range atomic order;
These vary from relatively simple structures for metals to exceedingly complex ones, as displayed by some of the ceramic and polymeric materials
When describing #crystalline #structures, #atoms (or ions) are thought of as being #solid #spheres having well-defined diameters.
This is termed the #atomic hard-sphere model in which spheres representing nearest-neighbor atoms touch one another.
An example of the hard-sphere model for the atomic arrangement found in some of the common elemental metals is displayed in Figure
In this particular case all the atoms are identical. Sometimes the term lattice is used in the context of #crystal #structures; in this sense#lattice means a three-dimensional array of points coinciding with atom positions (or sphere centers).