Which factor is intrinsic (internal) affecting diffusion?

• A. Atomic structure
• B. Grain size
• C. External pressure
• D. Temperature

Answer: (A)

Diffusion is governed by the internal landscape of the crystal—the atomic structure. The way atoms are arranged in the lattice, the type of lattice (how tightly they’re packed, the spacing between sites), and the bonding environment set the energy barriers that atoms must overcome to hop from one site to another. This migration energy and the available pathways (vacancies or interstitial sites) are intrinsic properties of the material’s lattice, so they determine how easily atoms can move and which diffusion mechanisms dominate.

Grain size, by contrast, comes from processing and represents a microstructural feature that affects diffusion mainly through grain boundaries, which provide fast diffusion paths not present in the perfect lattice. External pressure and temperature are environmental conditions that can alter diffusion rates, but they are not intrinsic aspects of the material’s atomic makeup.