# [DFTB-Plus-User] DFTB+ about the process for calculating relaxed density

이인성 (화학과) islee at unist.ac.kr
Tue May 30 11:33:13 CEST 2017

Hello, DFTB+ developers

I am a new user for dftb+ and I want to know about relaxed density matrix.

To obtain the information about the oscillator strength, we have to know relaxed density matrix.

And to obtain the relaxed density matrix, we have to know the dipole moment integrals.

Differentiation of the total energy with respect to the field F gives the dipole moment.

d_mu_nu = e * < chi_mu | r | chi_nu > = \partial(h_mu_nu) / \partial(field)

where d_mu_nu is dipole moment integrals, chi is AO, e is electron charge, and r is the electron coordinate vector.

I am sorry for low quality of upper equations.

Thus, I want to know 1. the analytic formula for d_mu_nu and 2. the process how dftb+ calculate this dipole moment for oscillator strength.

Thank you.

In Seong Lee
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