# A coupled-cluster method

State-universal coupled cluster ( SUCC ) method is one of several multi-reference coupled-cluster ( MR ) generalizations of single-reference coupled cluster method.

The wavefunction of the coupled-cluster theory is written as an exponential ansatz:

One possible improvement to the standard coupled-cluster approach is to add terms linear in the interelectronic distances through methods such as CCSD-R12.

A full list of approximate coupled-cluster methods is available on the website.

Other variants of the coupled-cluster theory, such as equation-of-motion coupled cluster and multi-reference coupled cluster may also produce approximate solutions for the excited states ( and sometimes ground states ) of the system.

More complicated coupled-cluster methods such as CCSDT and CCSDTQ are used only for high-accuracy calculations of small molecules.

to both sides of the coupled-cluster Schroedinger equations.

The classification of traditional coupled-cluster methods rests on the highest number of excitations allowed in the definition of.

Q-Chem can perform a number of general quantum chemistry calculations, such as Hartree-Fock, density functional theory ( DFT ) including time-dependent DFT ( TDDFT ), Møller – Plesset perturbation theory ( MP2 ), coupled cluster ( CC ), equation-of-motion coupled-cluster ( EOM-CC ), configuration interaction ( CI ), and other advanced electronic structure methods.

* J. Paldus, P. Piecuch, L. Polypow, B. Jeziorski, " Application of Hilbert-space coupled-cluster theory to simple ( H < sub > 2 </ sub >)< sub > 2 </ sub > model systems: Planar models ", Physical Review A, 47, 2738 ( 1993 ).

In addition to the method described in the section above, chlorine and radiochlorine were prepared by the electrolysis of a Af eutectic on the vacuum line, and by exchange of Af with molten Af.

This conjugate was passed twice through Dowex-2-chloride and treated with various tissue powders in the same manner as described for the indirect method.

The method of compiling the AIA and TR lists will be described later.

Although he described his method as translating " sometimes word for word, sometimes sense for sense ," Alfred's translation actually keeps very close to his original, although through his choice of language he blurred throughout the distinction between spiritual and secular authority.

In the 1990s, Jürgen Schmidhuber described an algorithmic theory of beauty which takes the subjectivity of the observer into account and postulates: among several observations classified as comparable by a given subjective observer, the aesthetically most pleasing one is the one with the shortest description, given the observer ’ s previous knowledge and his particular method for encoding the data.

Copper cathodes produced using this method are also described as electrolytic copper.

In 1738 The Dutch-Swiss mathematician Daniel Bernoulli published Hydrodynamica, in which he described the fundamental relationship among pressure, density, and velocity ; in particular Bernoulli's principle, which is one method to calculate aerodynamic lift.

The method had been described earlier by Adrien-Marie Legendre in 1805, but Gauss claimed that he had been using it since 1795.

This book's method was adopted by the University of Oregon, as described in The Oregon Experiment ( 1975 ), and remains the official planning instrument.

He described the Cold War: " We face a hostile ideology global in scope, atheistic in character, ruthless in purpose and insidious in method ..." and warned about what he saw as unjustified government spending proposals and continued with a warning that " we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military – industrial complex.

AT & Ts Compatibility Bulletin No. 105 described the product as " a method for pushbutton signaling from customer stations using the voice transmission path.

or equivalently ( as consistent with the " method " described above ):

According to Donald R. Hopkins ( 2002 ), Madhav included a special chapter on smallpox ( masūrikā ) and described the method of inoculation to protect against smallpox.

As one critic writes: " Pei has been aptly described as combining a classical sense of form with a contemporary mastery of method.

The document described the manner and frequency of their celebrations of the eucharist, the reason for and the method of excommunication, the requirement to subscribe to the confession of faith, the use of congregational singing in the liturgy, and the revision of marriage laws.

She named the project after a sign she saw in the abode of Pope Celestine V, which translates as ' a room of one's own ', and which Smith felt best described her solitary method of photography.

There are two exceptions to the method described above.

Pecorino Romano cheese, whose method of production was first described by Latin authors like Varro and Pliny the Elder about 2, 000 years ago, was first created in the countryside around Rome.

The Tesla method was described in New York in 1897.

Since in astronomical applications this measurement cannot be done directly, because that would require travelling to the distant star of interest, the method using spectral lines described here is used instead.

The method of least squares was first described by Carl Friedrich Gauss around 1794.

" Cromwell described his method of portraying Cochrane as always playing himself.

This method has been described as akin to squeezing a garden hose to gate the flow of water through the hose.

Artificial intelligence researcher Marco Dorigo described in 1997 a method of heuristically generating " good solutions " to the TSP using a simulation of an ant colony called ACS ( Ant Colony System ).

Even using the simple watermarking method described, it can be difficult to distinguish some watermarks.

This work gave a heat of formation of aluminum fluoride which closely substantiates a value which had been determined by a less direct method, and raises this property to 15 percent above that accepted a few years ago.

Up until recently, this heat pump method of warming air was efficient only in areas of mild winters and when outside temperatures were above 40 degrees.

The above method has the disadvantage that it can deviate from the standard alphabetical order that human users would expect, particularly due to the unexpected ordering of capital letters before all lower-case ones ( and possibly the unexpected treatment of spaces and other non-letter characters ).

* Redundant array of independent disks ( RAID )-This method generalizes the device mirroring above by allowing one device in a group of N devices to fail and be replaced with content restored ( Device mirroring is RAID with N = 2 ).

* Redundant array of independent disks ( RAID )-This method generalizes the device mirroring above by allowing one device in a group of N devices to fail and be replaced with content restored ( Device mirroring is RAID with N = 2 ).

A direct evaluation of either summation ( above ) requires operations for an output sequence of length N. An indirect method, using transforms, can take advantage of the efficiency of the fast Fourier transform ( FFT ) to achieve much better performance.

Bruun's algorithm ( above ) is another method that was initially proposed to take advantage of real inputs, but it has not proved popular.

Moseley's method in early X-ray spectroscopy was able to sort out the above chemical problems promptly, some of which had occupied chemists for a number of years.

One can verify this by the truth-table method referenced above.

Some enthusiasts may exclude one or more of the above on the basis of distribution method, name, or parentage, but all are free-form MUSH servers.

In the above ambiguity, class and its ancestors would be checked before class and its ancestors, so the method in would be inherited through.

) Nevertheless, even when several interfaces declare the same method signature, as soon as that method is implemented ( defined ) anywhere in the inheritance chain, it overrides any implementation of that method in the chain above it ( in its superclasses ).

Instead of going mad, they accepted terror as a normal administrative method and regarded obedience to all orders from above as a supreme virtue ....

Straight with Flush: if you cannot produce a good hand with method above with either the straight or the flush, then play the one with the higher top.

* Risk charting-This method combines the above approaches by listing resources at risk, threats to those resources, modifying factors which may increase or decrease the risk and consequences it is wished to avoid.

Steel guitar refers to a method of playing on a guitar held horizontally, with the strings uppermost and the bass strings towards the player, and using a type of slide called a steel above the fingerboard rather than fretting the strings with the fingers.

The best known method in this family is the Lin – Kernighan method ( mentioned above as a misnomer for 2-opt ).

When the method is applied to a sufficient number of people over the course of a project, the objections raised above become addressed: The sample size ceases to be small and usability problems that arise with only occasional users are found.

In the fourth example depicted above, the fifth stroke " closes out " a group of five, and is sometimes nicknamed the " herringbone " method of counting.