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MOLCAS SCF (Read 15013 times)
Gerrit-Jan Linker
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MOLCAS SCF
14.02.08 at 13:00:48
 
MOLCAS SCF
 
Program to generate closed shell SCF or Unrestricted SCF wavefunctions.  
 
Example input file for H2CO:
 
1. &SCF &END
2. Title
3. h2co
4. Charge
5. 0
6. End of input

 
Charge in line 4 and 5 is the total charge of the system.
 
See also:
MOLCAS
http://www.oraxcel.com/cgi-bin/yabb2/YaBB.pl?num=1202391381
MOLCAS SCF manual
http://www.teokem.lu.se/molcas/documentation/manual/node68.html
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« Last Edit: 19.11.08 at 19:38:09 by Gerrit-Jan Linker »  

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Re: MOLCAS SCF
Reply #1 - 09.03.08 at 22:12:19
 
For open shells UHF calculations can be done by specifying the UHF keyword. With spin symmetric start vectors a symmetric solution is found. Spin symmetry must be broken in order to obtain an open shell solution. This can be done manually by editing the orbitals or it could be attempted by using the SCRAMBLE keyword.
 
 
1. &SCF &END
2. Title
3. h2co
4. UHF
5. End of input
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« Last Edit: 06.06.13 at 15:05:58 by Gerrit-Jan Linker »  

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Re: MOLCAS SCF
Reply #2 - 21.03.08 at 23:17:43
 
MOLCAS SCF: UHF calculation with half integer charge
 
UHF calculcations are done by specifying the UHF keyword.
Using the Charge keyword only integer charge can be specified: i.e. 1,2,3,4,...
 
If half integer charge (+0.5 in my case) is required the orbitals need to be explicitly populated. It seems to lead to somehow unrealistic results as I find my HOMO with the half electron but with a lumo lower in energy...
 
Anyways, this is how to do it. In the SCF input use OCCUPIED and OCCNUMBERS.
 
With OCCUPIED you specify how many electrons go into each symmetry species. Repeat for beta spin if you do UHF.
I have a and b symmetry orbitals and would like to have 35 orbitals of a occupied and 32 of b. I have taken these numbers from a CHARGE +1 calculation. I specified:
 
UHF
OCCUPIED
35 32
35 32
 
Note I duplicated the row. The first row is for alpha spin and the second row is for beta spin.
 
Then with OCCNUMBERS you specify how many electrons go into each set of orbitals. I need to give 4 lines. The first with 35 occupation numbers, the second with 32, the third for orbitals a with beta spin with 35 again and finally a fourth for orbitals b with beta spin with 32. I specified (I've given 5 and 3 numbers to serve as example):
OCCNUMBERS
1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0
1.0 1.0 0.5
 
Note I have given the last orbital a 0.5 population. This is the half electron.
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Re: MOLCAS SCF
Reply #3 - 11.05.08 at 22:47:25
 
Using starting orbitals
 
Add the keyword LUMORB to use the starting orbitals from the INPORB file. To create a link called INPORB use the following command in the job file:
 
!ln -fs $Project.ScfOrb.autosaved INPORB
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« Last Edit: 14.08.08 at 12:44:56 by Gerrit-Jan Linker »  

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Re: MOLCAS SCF
Reply #4 - 14.08.08 at 12:48:24
 
DFT calculation
 
To do a DFT calculation the KSDFT keyword should be used followed (on the next line) by the functional to be used.
 
Example of a Molcas B3LYP DFT calculation:
 
1. &SCF &END    
2. Title    
3. h2co    
4. KSDFT
5. B3LYP
6. Charge    
7. 0    
8. End of input
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Unrestricted and Restricted DFT calculation
Reply #5 - 28.08.08 at 09:11:11
 
Unrestricted and Restricted DFT calculations
 
For systems with an uneven number of electrons an Unrestricted DFT calculation can be performed with MOLCAS. The UHF keyword needs to be used just like in HF calculations. To use Restricted DFT just omit the UHF keyword and the default RHF will be used.
 
An input example is the following B3LYP calculation on a system of charge +1 (assuming this leads to a uneven total number of electrons) using Unrestricted DFT.
 
1. &SCF &END    
2. Title    
3. testing  
4. KSDFT  
5. B3LYP  
6. Charge    
7. 0    
8. UHF
9. End of input  
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MOLCAS SCF open shell UHF input
Reply #6 - 15.05.13 at 22:56:28
 
MOLCAS SCF open shell UHF input
 
Open shell UHF input can be created. First run a UHF calculation using guess orbitals. Edit the optimised orbitals and use them as input (LUMORB). In the SCF set ITER to 0 to just check the input orbitals.
 
From the printout select the orbitals centered on fragments A and B.  
In the OCC section find out which orbital (the number) contains the outermost alpha electron.
In the UOCC section, do the same for the outermost beta electron.
 
In the ORB section of the orbitals file, identify the highest occupied MO and edit the vectors. Put a 1 for the basis functions on site A and a 0 for the basis function on site B.
In the UORB section do a similar operation for the beta electrons but put a 0 for site A basis functions and a 1 for site B basis functions.
 
 
 
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MOLCAS SCF: level shifter
Reply #7 - 11.11.13 at 10:14:06
 
MOLCAS SCF: level shifter
 
A level shifter can be used in Molcas SCF by specifying the homo lumo gap. For example to create a level shifter of 0.2 Eh:
 
hlgap
0.2
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MOLCAS SCF: Orthogonality violated
Reply #8 - 24.05.15 at 10:28:02
 
MOLCAS SCF: Orthogonality violated
 
Sometimes the SCF program stops with the error: orthogonality violated.
 
Decreasing the threshold for deleting linear depedent orbitals may solve the problem.  
This can be set through the OVLDelete parameter. Use a value e.g. of 1.0d-5
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