16

Aligning a molecule to a particular frame of reference (e.g., with the z-axis along a particular bond) is part of Avogadro for this reason: In Avogadro 1.x, there's an align tool You click one atom that will be set to the origin You click another atom that will be projected along the x, y, or z-axis You click 'align' and the molecular coordinates will be ...


6

I assume you're referring to eq 51 of the Hirata-Head-Gordon-Bartlett paper. One should note that these are not two-electron integrals, since there is only one spatial position; these are rather weighted four-center one-electron integrals. As always, the problem when you have four indices is that there is a huge number of integrals that come out, and you ...


2

I would agree that the best approach is to align your molecule in a way where your desired field is along one of the Cartesian axes. However, you can specify the direction/magnitude of the applied field using Gaussian. While the typical way of specifying a field Field=M+/-N only allows you to specify a multipole M and a magnitude N*.0001 a.u., you can give ...


1

Options 2 and 3 appear to be the same: the response is almost always the response of the energy, since the wave function is determined by the energy principle. To clarify: in many methods (e.g. Hartree-Fock or CC) one computes the derivative of the energy functional with respect to the property (e.g. polarizability or NMR shielding constants); this turns out ...


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