Difference between revisions of "Solution LAB2 guanine 3"
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(Created page with "* Back to the previous page: Electronic properties of isolated molecules#Exercise3 When dealing with cation pay attention to tot_charge nspin tot_magnetization") |
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| − | * Back to the previous page: [[Electronic properties of isolated molecules# | + | * Back to the previous page: [[Electronic properties of isolated molecules#Exercise 3]] |
| − | + | For calculation of E(N-1) we need to set the following flags in the &SYSTEM namelist: | |
| − | + | ||
| − | + | nspin=2 ! Note, now we have unpaired electrons: | |
| − | + | tot_charge=+1 ! charged system | |
| + | tot_magnetization=1 ! we need to set a total magnetisation | ||
| + | |||
| + | Also, the following option needs to be used for charged systems : | ||
| + | assume_isolated="mt" | ||
| + | |||
| + | Using ecutwfc=50 Ry and 35 au of cell size, | ||
| + | E_tot(N) = -193.48101821 Ry | ||
| + | E_tot(N-1) = -192.89782124 Ry | ||
| + | |||
| + | giving | ||
| + | IP = E_tot(N-1) - E_tot(N) | ||
| + | = 0.58319697 Ry | ||
| + | = 7.934861 eV | ||
| + | |||
| + | now much closer to the experimental value of 8.0-8.3 eV. | ||
| + | |||
| + | Interestingly, one can run the same set of calculations also using different functionals, | ||
| + | including GGAs (PBE), meta-GGAs (eg TPSS or SCAN), hybrids (PBE0), or HF itself. | ||
| + | |||
| + | In order to do this, you can force e.g. the functional from input, by using: | ||
| + | |||
| + | &SYSTEM | ||
| + | [...] | ||
| + | input_dft="PBE0" | ||
| + | / | ||
| + | |||
| + | How do -eps_HOMO and delta-scf values compare ? | ||
Latest revision as of 12:36, 26 March 2021
- Back to the previous page: Electronic properties of isolated molecules#Exercise 3
For calculation of E(N-1) we need to set the following flags in the &SYSTEM namelist:
nspin=2 ! Note, now we have unpaired electrons: tot_charge=+1 ! charged system tot_magnetization=1 ! we need to set a total magnetisation
Also, the following option needs to be used for charged systems :
assume_isolated="mt"
Using ecutwfc=50 Ry and 35 au of cell size,
E_tot(N) = -193.48101821 Ry E_tot(N-1) = -192.89782124 Ry
giving
IP = E_tot(N-1) - E_tot(N)
= 0.58319697 Ry
= 7.934861 eV
now much closer to the experimental value of 8.0-8.3 eV.
Interestingly, one can run the same set of calculations also using different functionals, including GGAs (PBE), meta-GGAs (eg TPSS or SCAN), hybrids (PBE0), or HF itself.
In order to do this, you can force e.g. the functional from input, by using:
&SYSTEM [...] input_dft="PBE0" /
How do -eps_HOMO and delta-scf values compare ?