New Features, New Chemistry
Gaussian 09 offers new features and performance enhancements which will enable you to model molecular systems of increasing size, with more accuracy, and/or under a broader range of real world conditions. We will introduce you to a few of these capabilities in detail here and outline the remainder.

Model Reactions of Very Large Systems with ONIOM
The ONIOM facility includes electronic embedding for MO:MM calculations whereby the electrostatic properties of the MM region are into account during computations on the QM region, and a fast, reliable optimization algorithm that takes the coupling between atoms in the model system and those only in the MM layer into account and uses microiterations for the MM layer between traditional optimization steps on the real system. Gaussian 09 provides many additional enhancements to the ONIOM facility, including the following:

¡ß Transition state optimizations.
¡ß Much faster IRC calculations.
¡ß Frequency calculations including electronic embedding.
¡ß Calculations in solution.
¡ß General performance enhancements.
¡ß Fully customizable MM force fields.
¡ß New implementations of AM1, PM3, PM3MM, PM6 and PDDG semi-empirical methods with true analytic gradients and frequencies (parameters also fully customizable).

Study Excited States in the Gas Phase and in Solution
Gaussian 09 includes many new features intended for studying excited state systems, reactions and processes:
¡ß Analytic time-dependent DFT (TD-DFT) gradients.
¡ß The EOM-CCSD method.
¡ß State-specific solvation excitations and de-excitations.
¡ß Franck-Condon and Herzberg-Teller analysis (and FCHT).
¡ß Full support for CIS and TD-DFT calculations in solution (equilibrium and non equilibrium).

Many More New Features
Among Gaussian 09¡¯s many other new features are the following:
¡ß Significantly enhanced solvation features: In addition to the excited state features mentioned above, the SCRF facility also
includes a new implementation incorporating a continuous surface charge formalism that ensures continuity, smoothness
and robustness of the reaction field, and which also has continuous derivatives with respect to atomic positions and external
perturbing fields. This results in faster, more reliable optimizations (taking no more steps than the gas phase) and accurate
frequency calculations in solution.
¡ß Analytic gradients for the Brueckner Doubles (BD) method.
¡ß Additional spectra prediction: analytic DFT first hyperpolarizabilities and numeric second hyperpolarizabilities, analytic
static and dynamic Raman intensities, analytic dynamic ROA intensities, improved anharmonic frequency calculations.
¡ß Population analysis of individual orbitals.
¡ß Fragment-based initial guess and population analysis.
¡ß Ease of use features: reliable restarts of many more calculation types, fragment definitions within molecule specifications,
freezing atoms by type, fragment, ONIOM layer and/or residue, selecting/sorting normal modes of interest during a
frequency calculation, saving/reading post-SCF amplitudes, saving/reading normal modes.
¡ß Many new DFT functionals, including ones incorporating long range corrections, empirical dispersion, and double hybrids.
¡ß Substantial performance improvements throughout the program, including optimizations for large molecules, frequency
calculations on large molecules (as much as 16x in parallel), IRC calculations (~3x faster), and optical rotations (~2x faster).