Diatomic molecules energy gradient

EOM-CCSD gradients were implemented in 1994 by Stanton and Gauss. Recent applications to the Si surface of C2H2, the Si state of tetrazine, the excitation spetrum of C3H2, and a computation of force field for the first excited state of benzene" illustrate the power of gradient methods for electronically excited states. Table 12 compares calculated EOM-CCSD geometries, vibrational frequencies, and adiabatic excitation energies for the first excited state of a few diatomic molecules with available experimental data. 

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