Basis set superposition error
- Basis set superposition error
In quantum chemistry, calculations of interaction energies are susceptible to basis set superposition error (BSSE) if they use finite basis sets. As the atoms of interacting molecules (or of different parts of the same molecule) or two molecules approach one another, their basis functions overlap. Each monomer "borrows" functions from other nearby components, effectively increasing its basis set and improving the calculation of derived properties such as energy. If the total energy is minimised as a function of the system geometry, the short-range energies from the mixed basis sets must be compared with the long-range energies from the unmixed sets, and this mismatch introduces an error.
Two methods exist to eliminate this problem. The chemical Hamiltonian approach (CHA) replaces the conventional Hamiltonian with one designed to prevent basis set mixing "a priori", by removing all the projector-containing terms which would allow basis set extension. The counterpoise approach (CP) calculates the BSSE by re-performing all the calculations using the mixed basis sets, through introducing "ghost orbitals", and then subtracts this error "a posteriori" from the uncorrected energy. Though conceptually very different, the two methods tend to give similar results.
See also
* Basis set (chemistry)
* Quantum chemistry
* Quantum chemistry computer programs
Wikimedia Foundation.
2010.
Look at other dictionaries:
Basis set (chemistry) — A basis set in chemistry is a set of functions used to create the molecular orbitals, which are expanded as a linear combination of such functions with the weights or coefficients to be determined. Usually these functions are atomic orbitals, in… … Wikipedia
Erreur De Superposition De Base — En chimie quantique, les calculs d énergies d interaction sont susceptibles de produire des erreurs de superposition de base (en anglais Basis set superposition errors notées BSSE) si elles sont effectuées à partir de bases finies. Lorsque les… … Wikipédia en Français
Erreur de superposition de base — En chimie quantique, les calculs d énergies d interaction sont susceptibles de produire des erreurs de superposition de base (en anglais Basis set superposition errors notées BSSE) si elles sont effectuées à partir de bases finies. Lorsque les… … Wikipédia en Français
Quantum error correction — is used in quantum computing to protect quantum information from errors due to decoherence and other quantum noise. Quantum error correction is essential if one is to achieve fault tolerant quantum computation that can deal not only with noise on … Wikipedia
Radiative transfer equation and diffusion theory for photon transport in biological tissue — Photon transport in biological tissue can be equivalently modeled numerically with Monte Carlo simulations or analytically by the radiative transfer equation (RTE). However, the RTE is difficult to solve without introducing approximations. A… … Wikipedia
Mathematics and Physical Sciences — ▪ 2003 Introduction Mathematics Mathematics in 2002 was marked by two discoveries in number theory. The first may have practical implications; the second satisfied a 150 year old curiosity. Computer scientist Manindra Agrawal of the… … Universalium
Quantum computer — A quantum computer is a device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, information is… … Wikipedia
dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or … Universalium
Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… … Universalium
analysis — /euh nal euh sis/, n., pl. analyses / seez /. 1. the separating of any material or abstract entity into its constituent elements (opposed to synthesis). 2. this process as a method of studying the nature of something or of determining its… … Universalium
