Messages

1

General Questions and Answers / Re: Error Problem in loading Density of States (DOS) 2D plot

« on: October 28, 2016, 21:00 »

I am having the same problem in 2016.2 version, do I need to change something manually?

2

General Questions and Answers / Re: Discrepency between Molecular energy levels and Fermi energy and #of electron

« on: March 21, 2016, 02:30 »

Thanks Zh, the second you solution that you mentioned solved my problem. Would you please explain a little bit more why do I need to use the spin polarized calculation? I tried to search for it but I couldn't find any answer.
 and do you think is there a better basis set that I can choose for my system? (I am currently using the Double Zeta Polarized)

Cheers

The calculated system is C59W. The pseudoptentials for C and W you used are generated for the normal valence electron configurations, i.e., C: 2s^2  2p^2 ( 4 electrons); W: 6s^2 5d^4 (6 electrons). So the total number of valence electrons is 59*4 + 6 = 242. We expect the 121th molecular level (i.e., index of 120 in your attached picture) is the highest occupied one.  From your results, this level seems to be degenerated with the 122th molecular level ((i.e., index of 121 in your attached picture).  In such situation, which is contrast to what I said in my last reply, the use of "0.1 k" for electron temperature is not suitable. It would lead to a problem in determining the position of the highest occupied level. This is what you have met in your calculations.

Solution:
1) If you keep the use of non-spin polarization calculation (number_of_spins=1), you have to increase the value of electron temperature.
2) If you use the spin-polarization calculation(i.e., number_of_spins= 2), you can use small value of electron temperature as you already used.

The 2nd way is recommended because the spin-polarization calculation would give more reliable results.

3

General Questions and Answers / Re: Discrepency between Molecular energy levels and Fermi energy and #of electron

« on: March 19, 2016, 22:07 »

Thanks for the reply. I used 0.1 k as the temperature in my system, are you suggesting to use smaller value than 0.1 k?
And you didn't answer why I'm getting different result using the same code, would you please explain this too.

If your molecule has HOMO-LUMO gap, you can use much smaller value   for "electron_temperature", i.e.,  which tends to  be fixed electron occupation.
 

4

General Questions and Answers / Discrepency between Molecular energy levels and Fermi energy and #of electron

« on: March 19, 2016, 00:32 »

Hello,
   I am encountering a weird problem with ATK when I use the code (attached) to calculate the MOE, Fermi energy and # of electron and I would appreciate if someone can explain this. the problem is when I use this code several times, each time the result changes even though the code has not been changed.you can see this in the "C59W MOE.png" picture file.
the difference in the Fermi energy and MOE is really small so I might be able to ignore that (still I would love to know why), but the occupancy numbers are vastly different and can change the total properties of system.

And I would appreciate any suggestion that can enhance the accuracy of the calculation for this system (C59W) .

Cheers,
Ehsan

5

General Questions and Answers / Re: Molecular Energy Levels

« on: March 13, 2016, 19:18 »

Thanks again for the reply.
These are some parameters that I used to calculate the Molecular energy levels of C59W and I attached the script too.
Exchange Correlation: None  ////////       Mesh Cutoff :75.0 Hartree
Poisson Solver: MG         ////////                 SCF Iterations: Yes
Basis Sets:   Carbon: FHI [Z=4] DoubleZetaPolarized        ////  Tungsten: FHI [Z=6] DoubleZetaPolarized
 exchange=DiracBloch,
 correlation=VoskoWilkNussair,
I tried to use lower electron temperature as you suggested, but now I have a new problem. first thing I noticed if I repeat a simulation without changing any of the parameters, the total #of electrons changes (e.g #e: 242.248413,  241.984365, 240.172426) while everything else including TEnergy, or Fermi stay constant. I would appreciate if you can explain this difference between the # of electron that appears in my calculation even though I am running the same script.

Thanks again for your time.

6

General Questions and Answers / Re: Molecular Energy Levels

« on: March 10, 2016, 22:45 »

These are the Molecular Energy Spectrum of a C60 molecule, after one of the carbon atom is replace by tungsten. So it is a C59W (optimized structure). Is it possible to indicate to LUMO and HOMO of a structure like this from the provided energy levels?
Thanks again for the reply.

What sort of analysis does this output come from? Does not look like a MolecularEnergySpectrum for a molecular configuration....

Occupancy = 2.0 means 2 electrons in that state, a spin-up and a spin-down electron (full occupancy). Without spin-polarization, anything less than 2 means partial or no occupancy.

But I do not understand how you can have partial occupancy in a molecular system. Would expect either 2 or 0, like in the MolecularEnergySpectrum below.

Code

+------------------------------------------------------------------------------+
| Molecular Energy Spectrum Report                                             |
---------------------------------------------------------------------------- |
| Fermi level = -4.550063e+00                                                  |
| Number of electrons = 52.000000                                              |
| Unit = eV                                                                    |
| Eigenenergies given relative to the Fermi Level                              |
+------------------------------------------------------------------------------+
   22  -4.396009e+00   2.000000e+00
   23  -4.265472e+00   2.000000e+00
   24  -2.548539e+00   2.000000e+00
   25  -2.350585e+00   2.000000e+00
   26   2.350626e+00   6.490006e-40
   27   2.521805e+00   8.641132e-43
   28   6.023727e+00   7.440152e-44
   29   6.490207e+00   7.440152e-44
   30   7.177419e+00   7.440152e-44
   31   7.301969e+00   7.440152e-44

7

General Questions and Answers / Molecular Energy Levels

« on: March 9, 2016, 19:09 »

Could someone please help me to Identify the LUMO/HOMO energy levels for this molecular structures? and explain what does 1.70E+00 or 1.96E-01 occupancy mean?

| Fermi level = -4.130596e+00 |                   | Fermi level = -3.854812e+00 |            
| Number of electrons = 242.000343 |         | Number of electrons = 246.000138 |            
                           
                           
110   -2.23E+00   2.00E+00                  110   -2.73E+00   2.00E+00      
111   -2.19E+00   2.00E+00                  111   -2.68E+00   2.00E+00      
112   -2.15E+00   2.00E+00                  112   -2.66E+00   2.00E+00      
113   -2.13E+00   2.00E+00                  113   -2.65E+00   2.00E+00      
114   -1.95E+00   2.00E+00                  114   -2.53E+00   2.00E+00      
115   -1.18E+00   2.00E+00                  115   -2.50E+00   2.00E+00      
116   -1.13E+00   2.00E+00                  116   -2.44E+00   2.00E+00      
117   -1.00E+00   2.00E+00                  117   -1.69E+00   2.00E+00      
118   -9.85E-01   2.00E+00                  118   -1.68E+00   2.00E+00      
119   -9.02E-01   2.00E+00                  119   -1.59E+00   2.00E+00      
120   -5.84E-04   1.01E+00                  120   -1.44E+00   2.00E+00      
121   5.66E-04   9.89E-01                  121   -1.41E+00   2.00E+00      
122   6.62E-01   1.49E-11                    122   -4.48E-02   1.70E+00      
123   7.29E-01   1.15E-12                     123    5.74E-02   1.96E-01      
124   8.83E-01   2.88E-15                  124   7.49E-02   1.05E-01      
125   1.22E+00   6.85E-21                  125   2.97E-01   2.08E-05      
126   1.72E+00   2.58E-29                  126   6.73E-01   1.00E-11      
127   1.86E+00   1.03E-31                  127   9.17E-01   7.91E-16      
128   1.98E+00   9.77E-34                  128   9.42E-01   3.04E-16      
129   2.49E+00   2.50E-42                  129   1.46E+00   7.18E-25      
130   2.60E+00   7.44E-44                  130   1.70E+00   5.53E-29      

Thanks

8

General Questions and Answers / Re: Electron Affinity/ Ionization Energy of Isolated Benzene

« on: March 1, 2016, 18:04 »

This question is about section 2 in the tutorial "Benzene Single-Electron Transistor" http://quantumwise.com/documents/tutorials/latest/BenzeneSET/index.html/index.html

In order to get the same numbers as shown in the tutorial, you need to set the Poisson Solver to Multigrid and the boundary conditions to Multipole. I realized yesterday that this is not shown explicitly in the tutorial, and we will add it when it is next updated.

Thank you very much!

9

General Questions and Answers / Electron Affinity/ Ionization Energy of Isolated Benzene

« on: February 29, 2016, 20:45 »

I tried to calculate the EA and IA of an  isolated benzene molecule by following the manual,but unfortunately there are differences between my results and the ones in the manual.

State      Charging Energy
+2:  Manual: -15.37  Me: -9.940
+1:  Manual: -9.15     Me:-7.29
0:    Manual:  2.34    Me:0.216
-1:   Manual:  8.39    Me:2.384


Total Energies
+2:  Manual: -1014.57   Me: -1022.27
+1:  Manual: -1030.3     Me:--1032.21
0:    Manual: -1039.45   Me:-1039.5
-1:   Manual:  -1037.11    Me: -1039.28
-2:  Manual:  -1028.72  Me: -1028.72

I did not change any parameters except the charge, as it was explained in the manual but still the total energy of my calculation is different from the ones in  manual, leading to different EA and EI. I would appreciate if someone can explain this discrepancy in the results.

Thanks

10

General Questions and Answers / Re: C59W and C59Pt

« on: February 25, 2016, 04:46 »

Thanks for the reply, I am not sure what do you mean by the basis set size but if you mean the density mesh cut-off, I tried for two different values (150 Rydberg and 18 Rydberg). the followings are more details about what I am doing:

1. I want to be able to calculate the Mulliken net charge for a C59Pt molecule.
2. these are some parameters that I used in my calculation: LDA , DiracBloch exchange and VoskoWikiNussairRPA correlation.
3.In my calculation the Mulliken charge for Pt atom is 9.893 for 150Ry and 9.863 for 18 Ry that means the net charge of 0.107 and 0.137 respectively, while this value in literature is much larger ( 0.618-1.3)
BTW, would you please explain why the change in the density mesh cutoff value can change the final result and what do you think is the suitable value for this system

Thanks!

11

General Questions and Answers / C59W and C59Pt

« on: February 24, 2016, 19:36 »

Hello,

what are the parameters that I need to consider to calculate the Mulliken population of C59Pt structure (C60 structure where one of the carbon is replaced by Pt). The net charge for the Pt calculated for my calculation is a lot larger in compare to the literatures.
I can provide more information if it is necessary.

Cheers,
Ehsan