Dear Ali, First of all, note that the GWW is implemented only at the gamma point, so it requires large supercells, (or better it is appropriate for non-crystalline systems). However the long-range parts of the symmetric dielectric matrix and of the screened-interaction can be calculated using k-points. With the code ph.x you are calculating the head and the wings of the symmetric dielectric matrix. E_HEAD are the head terms of the symmetric dielectric matrix calculated on the imaginary frequency axis (e.g. "E_HEAD : 58" is relative to the 58th frequency step). These terms together with the wings are calculated using linear response. Then, also the long range part (element G=0,G=0) of the screened interaction can also be calculated using a k-points grid. The calculated elements are <\Psi_i|G(i \tau)v|\Psi_i>, where \Psi_i are the KS states G(i\tau) is the KS Green function in imaginary time and v is the bare Coulomb interaction. The term "X energy 1" is the exchange energy relative to the 1st KS state.
> I am trying to use implemented approach GWW in espresso to obtain > quasiparticle state for bulk TiO2 ,but I didn,t succeed to get true band > gap by GW density of state. > I used 10 10 12 kmesh for k sampling but I don't know which file and which > rows contains dielectric constant. when I grep E_HEAD ,the last lines is > E_HEAD : 58 (-0.288322417972075195E-19,-0.347622164532722579E-06) > E_HEAD : 59 (0.136048521030191330E-19,-0.268035068560476896E-06) ..... ..... > what is these two columns? where do I look for dielectric constant? > also when I grep the energy in exchange file I see > X energy 1 -3.13056306094735648 > X energy 2 -3.13125888267243768 Best regards, P. Umari (Democritos) ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.
