In science and engineering, it refers to a method or calculation that starts from fundamental physical laws and principles, without relying on any prior experimental data or empirical assumptions. This means the calculation is built from the ground up, starting with the basic laws governing the system under study.
Here are some examples of how "ab initio" is used in different contexts:
* Ab initio calculations in quantum chemistry: These calculations use the laws of quantum mechanics to determine the electronic structure and properties of molecules, without relying on experimental data.
* Ab initio modeling in astrophysics: These models use fundamental physical laws to simulate the evolution of stars, galaxies, and other celestial objects.
* Ab initio design in engineering: This approach involves designing a product or system from scratch, based on first principles and without relying on existing designs or prototypes.
In general, ab initio methods are considered to be more accurate and reliable than methods that rely on empirical data or assumptions. However, they can also be more computationally demanding and time-consuming.