Gaussian package

The ab initio calculations are performed also using the Gaussian 98 package. Computations are carried out at the MP4 and CCSD(T) levels of theory. The He2-Br2 system is described using the r, Ri, R2,01,02, a) coordinate system, r is the bond length of Br2 Ri, R2 are the intermolecular distances of each He atom from the center of mass of Br-Br, 0i is the angle between the Ri and r vectors, while 02 is the one between R2 and r, and 7 is the angle between the Ri and R2 vectors. 

Fig. 7.5 Above Charge distribution on model for TFE-VAc dyad calculated using Gaussian 98 package, revision All note charges on protons next to carbonyl and CF3 group. Below Optimized binding geometries for the CO2 - TFE-VAc dyad using MP2/6-31-Hg(d)...

Figure 3. (A) Geometry and atom labeling of PPV oligomers. Molecular structure was optimized using the Austin model 1 (AMI) semiempirical modeP in Gaussian 98 package (B) Absorption spectrum of PPV(IO). Dashed line experimental absorption of a PPV thin Solid...

Figure 4. (A) Structures of the neutral N(n) and polar P(n) (substituted by the strongest acceptor) carotenoids. Molecular geometries were optimized using AM 1 modeP in Gaussian 98 package. Calculations were done for chain lengths of n = 5. 10. 20. and 40 double bonds (B) Variation of the bond-length alternation (top) and total charge Qa (bottom) along the chain in polar P(40) molecule (C) Linear absorption spectra calculated with line width r = 0.2 eV of the N(20) (dashed lines) and P(20) (solid lines) molecules contour plots of electronic modes which domi nate the absorption spectra of N(20) and P(20). Reprinted with permission from ref 81. Copyright 1997 American Chemical Society.

Figure 9. (A) Structures and atom labeling of naphthalene and bridged naphthalene dimer molecules. Molecular geometries were optimized using AMI model in Gaussian 98 package 2 (B) UV absorption spectra of the DN n series. Top experiment. Bottom linear absorption profile calculated with line width Fy = 0.2eK Computed absorption spectra are shown in arbitrary units Contour plots of electronic modes which dominate the absorption spectra of DN-n. The axis labels represent the individual carbon atoms as labeled in the molecular templates (A). Reprinted with permission from ref 342. Copyright 1999 National Academy of Sciences, U.S.A.

Similarly to Lanczos method for solving the RPA problem eq 2.15, Davidson s algorithm needs to be modified to take into account the block paired structure of eq 2.18 and scalar product eq Bl. The first RPA algorithm has been developed by Rettrup " and later improved by Olsen. The method has been further refined in ref 79, combined with TDDFT technique, and incorporated into Gaussian 98 package. We will follow ref 79 to describe this method. 

Ab initio quantum mechanical calculations these were calculated using the RHF/6-31G basis set of Gaussian 98 package on an SGI Octane workstation ... 

If carried out with a good basis set [6-31G(d) or better], the benefits of MPPT, carried out to second order (MP2), include moderate improvements in structures and relative energies and often significant improvement in the values of secondary properties such as dipole moments, vibrational frequencies, infrared and Raman absorption intensities, and NMR chemical shifts. Modem quantum chemistry codes such as the GAUSSIAN package incorporate analytical calculation of MP2 forces and force constants. Although it adds substantially to the time required to carry out the calculations, the results of MPPT usually make the extra effort worthwhile. 

Tel. 518-276-2678, e-mail breneman quant.chem.rpi.edu Computes electrostatic-potential-derived charges from ab initio wavefunctions generated by one of the Gaussian packages. UNIX and OpenVMS machines. 

To get an overview of the relevant potential energy surfaces, several stationary points of each system were calculated with the 6-311+G basis set and the B3LYP functional using the Gaussian package of programs [5]. For the structural identification of the expected species it was also necessary to obtain the calculated vibrational spectra. 

Cook describes the application a posteriori of literate programming methods to the last public release of the well known gaussian package, gaussian70, for molecular electronic structure calculations. 

I have used the Gaussian package with the coupled cluster method [CCSD(T), a procedure known as a rather reliable one, as described in Chapter 10 also, a reasonable quality of the atomic basis set 6-311G(d,p) was used see Chapter 8]. 

The original three parameters hybrid was suggested by Becke A. D., J. Chem. Phys. 98 (1993) p. 5648. The form implemented in Gaussian packages is slightly modified. 

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