Electronic World

Why do metals conduct electricity? Why is silicon a semiconductor?
Understanding material properties through electron behavior

What is a Band Gap?

When atoms gather to form a solid, electron energies form continuous 'bands'. The band gap is the energy difference between the 'valence band' where electrons reside and the 'conduction band' where electrons can move.

Metal

Bands overlap

Band gap = 0

gap

Semiconductor

Small gap

0 < gap < 3 eV

large gap

Insulator

Large gap

gap > 3 eV

Key Point:Materials with band gap = 0 are 'metals' that conduct electricity well. Materials with small band gaps are 'semiconductors' that can switch with temperature or light. This is what's used in smartphone and PC chips!

Conductors, Semiconductors, and Insulators

Conductor (Metal)

Examples: Copper, Gold, Silver, Iron
Feature: Electrons move freely
Uses: Wires, Electrodes
Band gap: 0 eV

Semiconductor

Examples: Silicon, Germanium
Feature: Conductivity changes with conditions
Uses: CPUs, Solar cells
Band gap: ~1-2 eV

Insulator

Examples: Diamond, Glass
Feature: Electrons cannot move
Uses: Insulation materials
Band gap: >3 eV

Fermi Level and DOS

Fermi Level (Ef)

At absolute zero (-273°C), this is the highest energy level occupied by electrons. It's a crucial parameter that determines the electrical and thermal properties of materials.

Fermi level in metals:
Since the valence and conduction bands overlap, electrons exist at the Fermi level and can conduct immediately.

Density of States (DOS)

Represents how many electron states exist at a given energy. In energy regions with high DOS, many electrons can exist.

DOS and properties:
High DOS at the Fermi level → tends to have higher specific heat and magnetic susceptibility.

Types of Magnetism

Electrons have a magnetic property called spin. The arrangement pattern of electron spins determines the magnetism of materials.

Ferromagnetic

All spins align in the same direction. Can become permanent magnets.

Examples: Iron (Fe), Cobalt (Co), Nickel (Ni)

FiM

Ferrimagnetic

Spins of different magnitudes align in opposite directions. Net magnetization exists.

Examples: Magnetite (Fe₃O₄)

AFM

Antiferromagnetic

Adjacent spins are opposite. No net magnetization.

Examples: Chromium (Cr), Manganese oxides

Non-magnetic

Spins pair up and cancel each other. No magnetism.

Examples: Copper (Cu), Gold (Au), Silver (Ag)

What is DFT Calculation?

Density Functional Theory (DFT) is a method to calculate the electronic structure of materials based on quantum mechanics. Material properties can be predicted through computer simulation without experiments.

About Materials Project

The electronic structure data on this site uses the Materials Project DFT calculation database. It's an open science project where researchers worldwide share their calculation results.

Data from Materials Project (https://materialsproject.org) | CC BY 4.0

See the Real Data

Compare electronic structure data for each element. Check detailed DFT calculation data in Layer 3 mode!

View Materials Science Data