Overview

An overview of materials methodology.

This section provides a list of methodologies used in computational materials science to calculate properties of materials.

What is a material?

The term materials is used quite loosely, and has become more inclusive as the materials science community branches out to various areas of physics and chemistry. The conventional textbook definition of materials is divided, by chemical composition, into three classes: metals, ceramics and polymers.

Metallic materials are composed of, as the name suggests, metals. This class of materials is commonly seen in applications where structural integrity is important; jet engines, for example, have to use an alloy of up to 15 types of metals to remain structurally sound despite the high temperature generated by combustion.

Ceramic materials are mostly oxides of metals. Some staple ceramic materials include Lead Zirconate Titanate (PZT) and CoO₂. The former is the most commonly used piezoelectric (this type of materials converts mechanical work into electrical work) while the latter is the most commonly used Lithium ion battery cathode.

Polymer materials are the result of polymerization of organic monomer molecules. As a relatively new materials class, polymers have received much research attention due to their versatility. Polymers are ubiquitious in modern life in the form of plastics. Furthermore, polymer research in materials science also branches out to biological areas like drug delivery and tissue regeneration.

Another way to classify materials is by their use case; in this scenario materials are classified into structural and functional materials. Structural materials serve to protect the structural integrity of something, for example, a car frame. Functional materials serve a particular function (other than supporting weight), for example: doped semiconductors which emit particular color of light when packaged as a light emitting diode (LED); battery elecrodes/electrolytes; piezoelectrics for accurate timekeeping, and magnetic materials used in medical technology like MRIs.

In short, materials science focuses on the joint of physics and chemistry and works on coming up with designs that satisfy a particular need in our real world.

What kind of properties do we care about?

Depending on the intended usage of our calculated data, there are different sets of properties that we care about:

• Electronic structure:

  • Band structure

  • Electronic density of states

  • Magnetism

  • Electronic charge density

    • Partial charges

    • Multipole moments (dipole, quadrupole, etc.)

  • Piezoelectricity

  • Dielectric constants

• Atomic structure:

  • Crystal structure

  • Elastic constants

  • Ionic conducivity / mobility

  • Phonon spectra

  • Thermodynamic equations of state

• Electron-phonon coupling and its effects on the above properties

And many more that we haven't mentioned here!

How do we calculate/predict these properties?

In computational materials science, we use Ab Initio (from first principles) methods to simulate the behavior of particles in the systems we're interested in. For materials data on the Materials Project, the majority of our work is done using Vienna Ab Initio Simulation Package (VASP), which primarily uses Density Functional Theory (DFT) to calculate many properties from first principles.