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 do more research in 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, has to use an alloy of up to 15 types of metals to withstand the high temperature generated by the combustion while still being able to stay structurally intact.
Ceramic materials are mostly oxides of metals, for the purpose of materials science. 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 results of polymerization of organic monomer molecules. As a relatively new member of the materials class, polymers have received much attention in the research space thanks to their versatility. Everyday plastic items, ranging from plastic bags, take out containers and Tupperware to water bottles, toys and Legos, are all polymers. Furthermore, polymer research in materials science also branch out to biological areas like drug delivery and tissue regeneration.
Another way to classify materials is by its usage case; in this scenario materials are classified into structural and functional materials. Structural materials, as the name suggests, serves to protect the structural integrity of something. A car frame, for example, would be a structural material. Functional materials, on the other hand, serves some kind of function (other than supporting weight, that is). The majority of modern-day materials science research lives in this functional materials space, ranging from semiconductors in computer chips, battery electrodes and OLEDs to piezoelectrics and MRI machines.
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.
For example, a materials scientist might be working on coming up with a semiconducting material that serves a certain purpose. They will be interested in looking at the electronic structure behavior of materials, such as band structure. Someone else might be interested in looking at piezoelectric properties, while others are interested in the migration behavior of a battery material. In short, depending on the interest, there is a range of properties we care about and calculate.

How do we calculate/predict these properties?

In computational materials science, we use Ab Initio (from first principle) 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 implements Density Functional Theory (DFT) to calculate all kinds of properties from first principle.