Computational packages

HyperChem is a versatile molecular modeler and editor and a powerful computational package. It offers many types of molecular and quantum mechanics calculations. 

In compensator design, hand calculation is cumbersome, and a suitable computer package, such as MATLAB is generally used. 

Although the correlation coefficient r would easily be calculated with the aid of a modern calculator or computer package, the following example will show how the value of r can be obtained. 

The dissemination of computers, and the diffusion of complex computational packages, has given origin to another type of members of group 111, the "molecular computers". 

To understand how such computer packages function, consider the simple flowsheet in Figure 13.13a. This involves an isomerization of Component A to Component B. The mixture of A and B from the reactor is separated into relatively pure A, which is recycled, and relatively pure B, which is the product. No byproducts are formed and the reactor performance can be characterized by its conversion. The performance of the separator is to be characterized by the recovery of A to the recycle stream (rA) and recovery of B to the product (rB). 

The electronic structure method used to provide the energies and gradients of the states is crucial in photochemistry and photophysics. Ab initio electronic structure methods have been used for many years. Treating closed shell systems in their ground state is a problem that, in many cases, can now be solved routinely by chemists using standardized methods and computer packages. In order to obtain quantitative results, electron correlation (also referred to as dynamical correlation) should be included in the model and there are many methods available for doing this based on either variational or perturbation principles [41],... 

The numerical methods for partial differential equations can be classified according to the type of equation (see Partial Differential Equations ) parabolic, elliptic, and hyperbolic. This section uses the finite difference method to illustrate the ideas, and these results can be programmed for simple problems. For more complicated problems, though, it is common to rely on computer packages. Thus, some discussion is given to the issues that arise when using computer packages. 

The second necessary ingredient in the primitive quasichemical formulation is the excess chemical potential of the metal-water clusters and of water by itself. These quantities p Wm — can typically be obtained from widely available computational packages for molecular simulation [52], In hydration problems where electrostatic interactions dominate, dielectric models of those hydration free energies are usually satisfactory. The combination /t xWm — m//, wx is typically insensitive to computational approximations because the water molecules coat the surface of the awm complex, and computational errors can compensate between the bound and free ligands. 

E., Gaita-Arino, A. Palii, A. (2014) An Updated Version of the Computational Package SIMPRE that Uses the Standard Conventions for Stevens Crystal Field Parameters. /. Comput. Chem., 35, 1930-1934. 

Practical design problems may need to take into account many additional factors, including the recycle of some reactants (such as hydrogen), residence time distribution, inhomogeneity of the packing, multiple reactions, approach to equilibria, and so on. All of these problems have been encountered before, and professional simulator routines for solving them are versatile, effective and as reliable as the data provided to them. At least half a dozen such computer packages are commercially available. 

There are commercial computer packages available for handling the network construction, interactions, and calculations involved in what, as will be shown below, is a complicated process. These packages are available for use on both mainframe and microcomputer systems. 

To maximize the usefulness of this approach, however, it would be desirable to reconstruct the data-coUection software and to formulate a computer package which can be more easily interfaced. This was not possible for a one-off development and the constraints imposed by the inherent software design had to be tolerated. 

Table 5.74 lists the main solid-solid reactions commonly adopted in geochemistry, with their respective AH°p AS°p p, AVp p, and AG°p p, calculated with the INSP and THERMO computer packages (Saxena, 1989). 

The oscillator strengths obtained for the different transitions studied in the present work with the RQDO methodology, and the use of the two forms of the transition operator, the standard one, and that corrected for core-valence polarization, are collected in Tables 1 to 8, where other data, from several theoretical and experimental sources, have been included for comparative purposes. The former comprise the large-scale configuration interaction performed with the use of the CIVS computer package [19] by Hibbert and Hansen [20] The configuration interaction (Cl) procedure of... 

In excerpt 3Y, the authors refer to computational results performed with the Gaussian suite of programs, a computational package used to calculate molecular ab initio or semiempirical electronic structure theory. Computational parameters (e.g., the basis set and level of theory) are included in the description. Do not worry if you do not understand the content of excerpt 3Y the language is intended for chemists with a computational or theoretical background. 

ROHF calculations are not well defined, and the reader is cautioned that this term has meanings that differ among workers. Some computational packages, GAMESS[46] is an example, in doing a single-atom calculation, do not treat the... 

Computer packages such as SAS can fit these models, provide estimates of the values of the b coefficients together with standard errors, and give p-values associated with the hypothesis tests of interest. These hypotheses will be exactly as Hqj, Hq2 and Hq3 in Section 6.3. Methods of stepwise regression are also available for the identification of a subset of the baseline variables/factors that are predictive of outcome. 

Finally note that in our considerations we have worked with groups of equal size. It is straightforward to adapt the calculations for unequal randomisation schemes and the computer packages mentioned earlier can deal with these. Altman (1991), Section 15.3 provides a simple method for adapting the standard sample size calculation to unequal group sizes as follows. If N is the calculated sample size based in an equal randomisation and k represents the ratio of the number of patients in one group compared to the other group, then the required number of patients for a A to 1 randomisation is ... 

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