semiempiricise

Semiempiricism is a term used in various scientific fields, particularly in chemistry and physics, to describe computational methods that combine theoretical principles with empirical data. These methods are designed to be more efficient and less computationally demanding than purely ab initio (from first principles) approaches, while still offering a higher level of accuracy than purely empirical models.

In computational chemistry, semiempirical methods are often used for calculating the electronic structure of molecules. They start with a theoretical framework, such as Hartree-Fock theory, but then simplify certain complex calculations by introducing approximations or using parameters derived from experimental measurements. These parameters are typically fitted to reproduce known properties of small molecules or atoms. This allows semiempirical methods to provide reasonable results for larger molecules where ab initio calculations would be prohibitively expensive.

The advantage of semiempirical methods lies in their speed and ability to handle larger systems. However, their accuracy is inherently limited by the approximations made and the quality of the empirical parameters used. They are generally not as accurate as high-level ab initio or density functional theory (DFT) methods, but they can be very useful for exploratory studies, initial screening of candidates, or in situations where computational resources are limited. Different semiempirical methods exist, each with its own set of approximations and parameterizations, leading to varying levels of accuracy and applicability to different types of chemical problems.