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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).
There is a paucity of reliable guidance on estimating sample sizes before starting the research, with a range of suggestions given. [ 16 ] [ 19 ] [ 20 ] [ 21 ] In an effort to introduce some structure to the sample size determination process in qualitative research, a tool analogous to quantitative power calculations has been proposed.
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. The Davidson correction does not give information about the wave function.
For example, the mass of a sample is an extensive quantity; it depends on the amount of substance. The related intensive quantity is the density which is independent of the amount. The density of water is approximately 1g/mL whether you consider a drop of water or a swimming pool, but the mass is different in the two cases.
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.
The following outline is provided as an overview of and topical guide to the scientific method: . Scientific method – body of techniques for investigating phenomena and acquiring new knowledge, as well as for correcting and integrating previous knowledge.
An integrated outline is a helpful step in the process of organizing and writing a scholarly paper (literature review, research paper, thesis or dissertation). When completed the integrated outline contains the relevant scholarly sources (author's last name, publication year, page number if quote) for each section in the outline.
Each entry below is an outline, an introduction to a subject structured as a hierarchical list of the essential points.Each of these outlines focuses on a science. Along with Wikipedia:Contents/Outlines, the outlines on Wikipedia form an all-encompassing outline of the knowledge of humankind.