Method keywords

In Gaussian, open shell calculations are requested by prepending the method keyword with a U (for unrestricted) similarly, closed shell calculations use an initial R (for example, RHF versus UHF, RMP2 versus UMP2 and so on). ... 

In the literature on synthesis and reactions, almost all provide NMR data along with other structural evidences, even though they are not categorized under NMR or experimental methods keyword search in Chemical Abstracts. The presence of two vicinal heteroatoms causes dissymmetry in the ring nucleus, thus affects the chemical shifts of both proton and carbon nuclei in the ring. The differences in the chemical shifts almost always enable one to elucidate the structure of an unknown isoxazole, on the basis of NMR alone. Of course one needs to consider the effects of substituents on the chemical shift. 

The E4T option to the UQCISD method keyword tells Gaussian to run fhe component MP4 calcdations at the MP4(SDTQ) level, rather than the default of MP4(SDQ). When you set up the QCISD(T) calculations for methane, include the additional option IOP(2/16=1) in the route section (which says to ignore any symmetry changes during the scan) and also include Gue s=(Always b() for the unrestricted casr. Mix requests that the HOMO and LUMO be mixed so as to destroy alpha-beta and spatial spin symmetries (this option is also useful for producing unrestricted wave functions for singlet systems), and Always says to recompute a new guess wavefunction at each point. 

Keywords d rec methods, indirect methods, rock properties, coring, core barrel, standard core analysis, special core analysis, slabbed core, sidewall samples, direct indications, microfossils, sonde, logging unit, invasion, mudcake, formation pressure measurement, fluid sampling, measurement while drilling, formation evaluation while drilling. 

Keywords deterministic methods, STOllP, GllP, reserves, ultimate recovery, net oil sands, area-depth and area-thickness methods, gross rock volume, expectation curves, probability of excedence curves, uncertainty, probability of success, annual reporting requirements, Monte-Carlo simulation, parametric method... 

The route section of a Gaussian input file specifies the kind of job you want to run as well as the specific theoretical method and basis set which should be used. All of these items are specified via keywords. Recall that the first line of the route section begins with a sign (or T to request terse output). 

Gaussian includes a facility for automatically generating a starting structure for a transition state optimization based upon the reactants and products that the transition structure connects, known as the STQN method. This feature is requested with the QST2 option to the Opt keyword. Input files using this option will include two title and molecule specification sections. The facility generates a guess for the transition structure which is midway between the reactants and products, in terms of redundant internal coordinates. 

Molecular frequencies depend on the second derivative of the energy with respect to the nuclear positions. Analytic second derivatives are available for the Hartree-Fock (HF keyword). Density Functional Theory (primarily the B3LYP keyword in this book), second-order Moller-Plesset (MP2 keyword) and CASSCF (CASSCF keyword) theoretical procedures. Numeric second derivatives—which are much more time consuming—are available for other methods. 

Predict the zero point or thermal energy by running a frequency job at the optimized geometry, using the same method and basis set. (Note that these two steps maybe run via a single Gaussian job via the Opt Freq keyword.)... 

Basis set keywords are not used for semi-empirical methods as they are inherent in the method s definition. 

Optimize the structure of acetyl radical using the 6-31G(d) basis set at the HF, MP2, B3LYP and QCISD levels of theory. We chose to perform an Opt Freq calculation at the Flartree-Fock level in order to produce initial force constants for the later optimizations (retrieved from the checkpoint file via OptsReadFC). Compare the predicted spin polarizations (listed as part of the population analysis output) for the carbon and oxygen atoms for the various methods to one another and to the experimental values of 0.7 for the C2 carbon atom and 0.2 for the oxygen atom. Note that for the MP2 and QCISD calculations you will need to include the keyword Density=Current in the job s route section, which specifies that the population analysis be performed using the electron density computed by the current theoretical method (the default is to use the Hartree-Fock density). 

Compute the isotropic hyperfine coupling constant for each of the atoms in HNCN with the HF, MP2, MP4(SDQ) and QCISD methods, using the D95(d,p) basis set Make sure that the population analysis for each job uses the proper electron density by including the Density=Current keyword in the route section. Also, include the 5D keyword in each job s route sectionfas was done in the original study). 

Beginning with the final optimized structure from step 1, obtain the fii equilibrium geometry using the fuU MP2 method—requested with t MP2(Full keyword in the route section—which includes inner sh electrons. The 6-31G(d) basis set is again used. This geometry is used 1 all subsequent calculations. 

C=C stretch 80 C-13 chemical shifts 22, 53 C60 31,32 C60O isomers 54 carbon dioxide 120, 182 carbon monoxide 175,191 carbonyl series 84 carbonyl stretch 84, 220 in solution 244 Carmichael 136 Carpenter 152, 196 Cartesian coordinates 52, 286, 287 CASSCF keyword 228 CASSCF method 228,229,230,231, 232,233, 234,235 state-averaged 233... 

CBS extrapolation 155, 278 CBS methods 10, 96, 155 cost vs. G2 methods 159 CBS-4 method 155 CBS-Q method 155 CCSD keywords 114 CH bond dissociation 186 charge xxxv, xlii, 15, 286 predicted atomic li charge distribution 20 Cheeseman 53 chlorine (atomic) 137, 159 chlorobenzene 165 chromium hexacarbonyl 52 Cioslowski 198 CIS keyword... 

QCI methods 117 QCISD keywords 9,114 E4T option 186 quadratic Cl methods 114 quadrupole moment 21 quotation li... 

SCRF keyword 239 input for 239 options 239 SCRF methods... 

Units keyword 14, 34 Bohr option 287 Radian option 287 unrestricted methods 10 user initialization files xxxiii... 

Keywords abinitio methods, FMO (molecular orbital), hefero-Diels-Alder reaction, transition state structure... 

Kaneko C., Katagiri N., Nomura M., Sato H. A New Method for the Stereoselective Synthesis of Nucleosides by Means of Sodium Borohydride Mediated Reductive C-C or C-N Bond Cleavage Reaction Isr. J. Chem. 1991 31 247-259 Keywords carbohydrates... 

The first chapter presents the general aspects of the reaction Chapters 2-6 illustrate the various methods and their applications in organic synthesis. At the end of each chapter a list of graphically abstracted Diels-Alder reactions is presented to show selected synthetic applications of the specific methodology. The discussion of the various topics is not exhaustive because our aim has been to emphasize the synthetic potential of each method. Chapter 7 reports a list of books, reviews, monographs and symposia proceedings which have appeared since 1990 and an index of keywords to help the reader find a particular paper of interest. 

Keywords optical telescopes, off axisaspheres, polishing methods... 

However, if one lacks access to these, one may consult Chemical Titles and the keyword index (p. 1611) at the end of each issue of CA. In these cases, of course, it is necessary to know what name might be used for the compound. The name is not necessary for Index Chemicus (p. 1622) one consults the formula indexes. However, these methods are far from complete. Index Chemicus lists primarily new compounds, those which would not have been found in the earlier search. As for chemical Titles, the compound can be found only if it is mentioned in the title. The keyword indexes in CA are more complete, being based on internal subject matter as well as title, but they are by no means exhaustive. Furthermore, all three of these publications lag some distance behind the original journals. To locate all references to a compound after the period covered by the latest semiannual formula index of CA, it is necessary to use CAS-online. 

Keywords QM/MM methods, Jarzynski approximation, Enzyme mechanisms... 

Keywords Coarse-graining, Force-matching, Effective fragment potential method, Molecular... 

Keywords Ab initio QM/MM method, Pseudobond approach, Enzyme catalysis, Reaction... 

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