Quantities defined in X_s.F
Posted: Sat Aug 15, 2009 10:08 am
Dear Developers:
My question is still about the response function programmed in TDDFT module of yambo.
I looked through two subroutines :O_driver.F and X_s.F, and have a confusion about quantities defined in X_s.F . Would you please do me a favor for this issue ?
I learned from X_s.F that it solves Dyson equation for $\chi$ from $\chi_0$ which is stored in X_mat. My confusion is about the last description for $\chi$:
As far as i know, the solution for Dyson equation should be
$\chi=(1-\chi_0\upsilon-\chi_0 f_{xc})^{-1}\chi_0$.
My question is why we need multiply a quantity like Coulomb potential
for X_mat ? In this situation, does X_mat store the exact information for the response function $\chi$ ? Or other attentions need pay to ?
In O_driver.F , I found the expression the $\epsilion_M$
exactly follows the formula $\epilsion_M=1/(1+\upsilon\chi)$ . Therefore, in X_s.F why we perform a more calculation over X_mat as
Thanks in advance!
Regards,
Hai-Ping
My question is still about the response function programmed in TDDFT module of yambo.
I looked through two subroutines :O_driver.F and X_s.F, and have a confusion about quantities defined in X_s.F . Would you please do me a favor for this issue ?
I learned from X_s.F that it solves Dyson equation for $\chi$ from $\chi_0$ which is stored in X_mat. My confusion is about the last description for $\chi$:
Code: Select all
X_mat(i1,i2,iw)=X_mat(i1,i2,iw)*4.*pi/bare_qpg(iq,i1)/bare_qpg(iq,i2)
$\chi=(1-\chi_0\upsilon-\chi_0 f_{xc})^{-1}\chi_0$.
My question is why we need multiply a quantity like Coulomb potential
Code: Select all
4.*pi/bare_qpg(iq,i1)/bare_qpg(iq,i2)
In O_driver.F , I found the expression the $\epsilion_M$
Code: Select all
X_epsilon(2,fr(1):fr(2))=1./(X_mat(1,1,:)*bare_qpg(iq,1)**2/Q_sq_modulus+1.)
Code: Select all
X_mat(i1,i2,iw)=X_mat(i1,i2,iw)*4.*pi/bare_qpg(iq,i1)/bare_qpg(iq,i2)
Regards,
Hai-Ping