Tamm-Dancoff approximation functions

As it is not possible to obtain TDDFT-SS results, the results refer to CIS method. In fact, this method can be obtained from two points of view one is to consider the method as a standard Cl, in which the wave function of the excited state is constructed by single excitations from the HF determinant and thus a SS solvent response can be obtained the other is to consider CIS as the result of the Tamm-Dancoff approximation applied to the linear response equation based on the HF wave function. The two ways of looking at the CIS method give the same equations in vacuo, but, as discussed above, they differ for molecules in solution due to the nature of the effective Hamiltonian. 

J. Hutter (2003) Excited state nuclear forces from the Tamm-Dancoff approximation to time-dependent density functional theory within the plane wave basis set framework. J. Chem,. Phys. 118, p. 3928... 

FOCI - first-order configuration interaction. Outer valence Green s function. Extended two-particle-hole Tamm-Dancoff approximation. 

Liu J, Liang W (2011) Analytical Hessian of electronic excited states in time-dependent density functional theory with Tamm-Dancoff approximation. J Chem Phys 135 014113... 

SAOP functional, all-electron calculation, COSMO spin-flip transitions have been calculated within the Tamm-Dancoff approximation. 

In the following it will be outlined, how the parity violating potentials are computed within a sum-over-states approach, namely on the uncoupled Hartree-Fock (UCHF) level, and within the configuration interaction singles approach (CIS) which is equivalent to the Tamm-Dancoff approximation (TDA), that avoids, however, the sum over intermediate states. Then a further extension is discussed, namely the random phase approximation (RPA) and an implementation along similar lines within a density functional theory (DFT) ansatz, and finally a multi-configuration linear response approach is described, which represents a systematic procedure that... 

The interpretation of the experimental spectrum of 1 <1983CPL(97)94> has been reconsidered using Green s function (GF) and the nondiagonal Tamm-Dancoff approximation (TDA), as well as with multireference doubleexcitation configuration interaction (MRD-CI) calculations <1998CPH(228)39>. This paper also offers the following information about the parent 1 ... 

Density Functional Theory within the Tamm-Dancoff Approximation. 

A different analysis applies to the LR approach (in either Tamm-Dancoff, Random Phase Approximation, or Time-dependent DFT version) where the excitation energies are directly determined as singularities of the frequency-dependent linear response functions of the solvated molecule in the ground state, and thus avoiding explicit calculation of the excited state wave function. In this case, the iterative scheme of the SS approaches is no longer necessary, and the whole spectrum of excitation energies can be obtained in a single run as for isolated systems. 

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