Semi-empirical quantum chemistry method

Semi-empirical <a href="/facts/Quantum_chemistry/H9AXV0lx">quantum chemistry</a> methods are based on the <a href="/facts/Hartree%E2%80%93Fock/U9mlRWVR">Hartree–Fock</a> formalism, but make many approximations and obtain some parameters from empirical data. They are very important in <a href="/facts/Computational_chemistry/KyuCgRV3">computational chemistry</a> for treating large molecules where the full Hartree–Fock method without the approximations is too expensive. The use of empirical parameters appears to allow some inclusion of <a href="/facts/Electron_correlation/1XpBFce2">electron correlation</a> effects into the methods.
Within the framework of Hartree–Fock calculations, some pieces of information (such as two-electron integrals) are sometimes approximated or completely omitted. In order to correct for this loss, semi-empirical methods are parametrized, that is their results are fitted by a set of parameters, normally in such a way as to produce results that best agree with experimental data, but sometimes to agree with <a href="/facts/Ab_initio_quantum_chemistry_methods/Rwuu2At1">ab initio</a> results.

Semi-empirical quantum chemistry method open-in-new

Semi-empirical quantum chemistry method