Dear M. Inukai, 1. num_eign = number of eigenstates (excitations) which will be computed. This parameter must be chosen based on how large energy range for the spectrum the user is interested in. The bigger the energy range, the larger num_eign is. A priori it is not possible to guess this number, because it depends on the system. Try with some reasonable numbers (say, 5, 10, or 15) and then check whether this is enough to obtain a converged spectrum in the energy range of interest.
2. 'num_basis_max' is the maximum number of basis allowed in the subspace. In every Davidson iteration the number of basis used in the subspace is increased by num_init. When num_basis_max is reached, a discharging routine is called (this variable determines the memory requirement). The larger the parameter num_eign, the larger num_basis_max would be needed. Try with some reasonable numbers, run test calculations, and then increase/decrease num_basis_max based on your observations. Use examples in TDDFPT to get an idea about typical values of this parameter. 3. 'ecutfock' is the kinetic energy cutoff (Ry) for the exact exchange operator in the exact-exchange (EXX) type calculations. The meaning of this parameter is the same as in the PW code (pw.x), hence see the documentation in PW/Doc. The value of ecutfock cannot be smaller than ecutwfc. 4. 'itermax0' generally you can use the same number that you computed with turbo_laczos (itermax). 5. 'p_nbnd_occ and p_nbnd_virt' if you are interested only in energy and absorption spectrum, it is not necessary to use all occupied and virtual orbitals. Using all states is useful only if you are interested in the interpretation of the eigenstates. 6. 'pseudo_hermitian' When you use .FALSE., the code will be 2 times slower but the result must be the same. So it is always recommended to use .TRUE. unless it does not work for some reasons. The .FALSE. option was implemented first, and hence it is still kept in the code for the case when .TRUE. does not work. 7. 'CH4-BOND' this is obsolete and will be removed in the next release of QE. The meaning of "project", "absorbtive", and "dispersive" is not documented, it was introduced by Osman Baris Malcioglu around ~2011 (CPC 182, 1744 (2011)). These parameters are related to the calculation of the response charge density. You may try either to understand what does these keywords mean by looking into the code or try to contact Baris and ask him directly. Best regards, Oscar Baseggio - postdoctoral researcher, SISSA, Trieste, Italy Iurii Timrov - postdoctoral researcher, EPFL STI IMX THEOS, Lausanne, Switzerland ________________________________ From: users <[email protected]> on behalf of 犬飼 学 <[email protected]> Sent: Monday, November 26, 2018 2:17:37 AM To: [email protected] Subject: [QE-users] How to decide value of TDDFPT variables Dear developers Although I have red *.html in Doc (TDDFPT), I do not understand same variables in detail. Would you tell me any advices ? ---------- How do I decide 'num_eign', 'num_basis_max' and 'ecutfock' in *.dav-in ? How do I decide 'itermax0' in *.tddfpt_pp-in ? I set number of eigenvalue (<= EF) to p_nbnd_occ and set number of eigenvalue (>= EF) to p_nbnd_virt ? Is it best ? What do absorbtive and dispersive mean in CH4-BOND ? What does 'project' mean in CH4-BOND ? When do I use pseudo_hermitian=.false. -------- Best Regards, M. Inukai _______________________________________________ users mailing list [email protected] https://secure-web.cisco.com/19GAnZJq8KAnok_kIcfsPVX2cFnQjBcHHDJ1Me3k4GB8ARlEdR_PSsXj3f6NZyAT6Br-Z1c4M6lziWmaSbgvcxL9M3XKiEgWPD1igTAi13jQZbMm5p4u0EnzwrDrY2ibWKUX5hVu18-Ts5EFmwEzzvC9nDnsbHc6YjDo5Et3aY88Vevq_-ssnwzwbgNpjHU46HYluK2AHThecFDzDpc-oJNgB2jpBPVFQO4FvpnndUJhPwEMPLCBswmGae7CEu_hB9sPsX1b11-Z8fjViDo9S1I8reS_hReQeZPxnuAbWbltmhNnGRJgokkgoaER3T_C8MQIDwENW0HZ85yYfRfg9jg/https%3A%2F%2Flists.quantum-espresso.org%2Fmailman%2Flistinfo%2Fusers
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