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In quantum chemistry, size consistency and size extensivity are concepts relating to how the behaviour of quantum-chemistry calculations changes with the system size. Size consistency (or strict separability) is a property that guarantees the consistency of the energy behaviour when interaction between the involved molecular subsystems is nullified (for example, by distance).
Davidson correction improves both size consistency and size extensivity of CISD energies. [2] [4] Therefore, Davidson correction is frequently referred to in literature as size-consistency correction or size-extensivity correction. However, neither Davidson correction itself nor the corrected energies are size-consistent or size-extensive.
The choice of the exponential ansatz is opportune because (unlike other ansatzes, for example, configuration interaction) it guarantees the size extensivity of the solution. Size consistency in CC theory, also unlike other theories, does not depend on the size consistency of the reference wave function.
Quadratic configuration interaction [1] (QCI) is an extension of configuration interaction [2] that corrects for size-consistency errors in single and double excitation CI methods (CISD). [ 3 ] Size-consistency means that the energy of two non-interacting (i.e. at large distance apart) molecules calculated directly will be the sum of the ...
1. Stress. Hair loss or hair thinning after a hysterectomy is typically due to a condition called telogen effluvium, which happens when a major stressor to the body disrupts the normal hair growth ...
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