Application
Davidson correction is very popular due to its low computational cost. The correction improves contribution of electron correlation to the energy. The size-consistency and size-extensivity problems of truncated CI are alleviated but still exist. In small molecules, accuracy of the corrected energies can be similar to results from coupled cluster theory calculations.
Davidson correction does not give information about wave function. Therefore it cannot be used to correct wave-function-dependent quantities such as dipole moment, charge density and vibronic couplings. Analytical gradients for Davidson corrections are in general not available in quantum chemistry programs.
As with other perturbative approaches, Davidson correction is not reliable when the electronic structure of CISD and the reference Hartree-Fock wave functions are significantly different. The correction is invalid, when is not close to 1. This happens when multi-reference character is significant or when CISD is used to calculate a state that is not the reference state, for example, an excited state or a state with different spin multiplicity.
Read more about this topic: Davidson Correction
Famous quotes containing the word application:
“By an application of the theory of relativity to the taste of readers, to-day in Germany I am called a German man of science, and in England I am represented as a Swiss Jew. If I come to be regarded as a bête noire the descriptions will be reversed, and I shall become a Swiss Jew for the Germans and a German man of science for the English!”
—Albert Einstein (1879–1955)
“It is known that Whistler when asked how long it took him to paint one of his “nocturnes” answered: “All of my life.” With the same rigor he could have said that all of the centuries that preceded the moment when he painted were necessary. From that correct application of the law of causality it follows that the slightest event presupposes the inconceivable universe and, conversely, that the universe needs even the slightest of events.”
—Jorge Luis Borges (1899–1986)
“Science is intimately integrated with the whole social structure and cultural tradition. They mutually support one other—only in certain types of society can science flourish, and conversely without a continuous and healthy development and application of science such a society cannot function properly.”
—Talcott Parsons (1902–1979)