Solution LAB2 guanine 3: Difference between revisions
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* Back to the previous page: [[Electronic properties of isolated molecules#Exercise 3]] | * Back to the previous page: [[Electronic properties of isolated molecules#Exercise 3]] | ||
For calculation of E(N-1): | For calculation of E(N-1) we need to set the following flags in the &SYSTEM namelist: | ||
tot_charge=+1 !charged system | |||
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" | 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 10:36, 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 ?