The words exact and perfect do not appear here, as very few aspects of chemistry can be computed exactly. However, almost every aspect of chemistry can be described in a qualitative or approximate quantitative computational scheme.
Molecules consist of nuclei and electrons, so the methods of quantum mechanics apply. Computational chemists often attempt to solve the non-relativistic Schrödinger equation, with relativistic corrections added, although some progress has been made in solving the fully relativistic Dirac equation. In principle, it is possible to solve the Schrödinger equation in either its time-dependent or time-independent form, as appropriate for the problem in hand; in practice, this is not possible except for very small systems. Therefore, a great number of approximate methods strive to achieve the best trade-off between accuracy and computational cost.
Accuracy can always be improved with greater computational cost. Significant errors can present themselves in ab initio models comprising many electrons, due to the computational expense of full relativistic-inclusive methods. This complicates the study of molecules interacting with high atomic mass unit atoms, such as transitional metals and their catalytic properties. Present algorithms in computational chemistry can routinely calculate the properties of molecules that contain up to about 40 electrons with sufficient accuracy. Errors for energies can be less than a few kJ/mol. For geometries, bond lengths can be predicted within a few picometres and bond angles within 0.5 degrees. The treatment of larger molecules that contain a few dozen electrons is computationally tractable by approximate methods such as density functional theory (DFT).
There is some dispute within the field whether or not the latter methods are sufficient to describe complex chemical reactions, such as those in biochemistry. Large molecules can be studied by semi-empirical approximate methods. Even larger molecules are treated by classical mechanics methods that employ what are called molecular mechanics. In QM/MM methods, small portions of large complexes are treated quantum mechanically (QM), and the remainder is treated approximately (MM).
Read more about this topic: Computational Chemistry
Other articles related to "accuracy":
... rigorous algorithm for calculation of π to any accuracy ... Liu Hui's own calculation with a 96-gon provided an accuracy of five digits π ≈ 3.1416 ... algorithm to calculate π to any required accuracy based on bisecting polygons he calculated π to between 3.141024 and 3.142708 with a 96-gon he suggested that 3.14 was ...
... using local names for the creator or highest deity, conceptualizing accuracy as semantic rather than phonetic ... The limited number of Sacred Name Bibles suggests that phonetic accuracy is not considered to be of importance by mainstream Bible translators ...
... The partial sum has only one digit accuracy, while six-figure accuracy requires summing about 400,000 terms ... and Shanks transformation results, clearly showing the improved accuracy and convergence rate 0 4.00000000 — — — 1 2.66666667 3.16666667 — — 2 3.46666667 3.1333333 ...
... Olsen won the Gold Medal in Women's Individual Accuracy at the XIX World Parachuting Championships in Sweden in 1988 ... Kangas, Eileen Vaughn, and Bev Watson, won the Silver Medal in Women's Team Accuracy at the XVI World Parachuting Championships in Czechoslovakia, after which they posed in bikinis in a 1982 issue of ... She also served as Chief Judge in Style Accuracy at the 2004 US National Skydiving Championships ...
Famous quotes containing the word accuracy:
“The child who has been taught to make an accurate elevation, plan, and section of a pint pot has had an admirable training in accuracy of eye and hand.”
—Thomas Henry Huxley (182595)
“As for farming, I am convinced that my genius dates from an older era than the agricultural. I would at least strike my spade into the earth with such careless freedom but accuracy as the woodpecker his bill into a tree.”
—Henry David Thoreau (18171862)
“Such is the never-failing beauty and accuracy of language, the most perfect art in the world; the chisel of a thousand years retouches it.”
—Henry David Thoreau (18171862)