What do bulk modulus and elastic properties tell me?

Elastic properties describe how a material responds to mechanical stress:

Bulk Modulus (K)

Resistance to uniform compression. Higher K means the material is harder to compress.

• Diamond: ~440 GPa (extremely incompressible)
• Steel: ~160 GPa
• Lead: ~46 GPa (easily compressed)

Shear Modulus (G)

Resistance to shape change. Higher G means more rigid.

Young's Modulus (E)

Resistance to stretching/compression along one axis. The most commonly reported mechanical property.

Poisson's Ratio (v)

How much a material expands laterally when compressed. Ranges from -1 to 0.5:

• ~0.3: Typical for metals
• ~0.2: Ceramics
• < 0: Auxetic materials (rare, expand laterally when compressed)

Pugh's Ratio (K/G)

Predicts ductile vs. brittle behavior:

• K/G > 1.75: Ductile (metals)
• K/G < 1.75: Brittle (ceramics)

Note: Elastic properties are not available for all materials in the database. They require separate elastic constant calculations beyond standard structure relaxation.