The manual says "Geminal and multigeminal wave function parameters are dened in the GEMINAL toplevel block of
the parameters.casl le. More information about the specics of these wave functions and on the
format of the casl block is available on request."
I would like to try geminal wave function for some molecules with strong multireference character, but who should I ask for?
with best regards,
Fan
Multigeminal wave functions

 Posts: 52
 Joined: Thu Jan 30, 2014 1:25 am
Re: Multigeminal wave functions
Hi Fan,
Each geminal in the MAGP wave function requires norb x norb parameters and a global coefficient. So if you have two orbitals in your basis, you would specify a singlegeminal wave function in parameters.casl as:
Input keywords opt_orbitals and opt_detcoeff control whether g_*,* and c are optimized.
The MAGP wave function was implemented as part of a PhD project in 2014 and, while it worked fine then in tests, it has seen little use since. Let us know if you encounter problems.
Best,
Pablo
Each geminal in the MAGP wave function requires norb x norb parameters and a global coefficient. So if you have two orbitals in your basis, you would specify a singlegeminal wave function in parameters.casl as:
Code: Select all
GEMINAL:
Geminal 1:
Parameters:
c: [ 1.d0 , fixed ]
g_1,1: [ 1.d0 , optimizable ]
g_1,2: [ 0.d0 , optimizable ]
g_2,1: [ 0.d0 , optimizable ]
g_2,2: [ 1.d0 , optimizable ]
The MAGP wave function was implemented as part of a PhD project in 2014 and, while it worked fine then in tests, it has seen little use since. Let us know if you encounter problems.
Best,
Pablo
Hey there! I am using CASINO.
Re: Multigeminal wave functions
Dear Pablo,
Thanks very much for your help. Do you any example on using it?
I calculated reaction energy for O3 > O + O2 using singleSlaterJastrow wavefunction in DMC and the result is rather poor. With CASSCFJastrow wavefunction in DMC, the result is improved, but still unsatisfactory. I would like to try some other trial wavefunction such as JAGP in DMC.
with best regards,
Fan
Thanks very much for your help. Do you any example on using it?
I calculated reaction energy for O3 > O + O2 using singleSlaterJastrow wavefunction in DMC and the result is rather poor. With CASSCFJastrow wavefunction in DMC, the result is improved, but still unsatisfactory. I would like to try some other trial wavefunction such as JAGP in DMC.
with best regards,
Fan
Pablo_Lopez_Rios wrote:Hi Fan,
Each geminal in the MAGP wave function requires norb x norb parameters and a global coefficient. So if you have two orbitals in your basis, you would specify a singlegeminal wave function in parameters.casl as:
Input keywords opt_orbitals and opt_detcoeff control whether g_*,* and c are optimized.Code: Select all
GEMINAL: Geminal 1: Parameters: c: [ 1.d0 , fixed ] g_1,1: [ 1.d0 , optimizable ] g_1,2: [ 0.d0 , optimizable ] g_2,1: [ 0.d0 , optimizable ] g_2,2: [ 1.d0 , optimizable ]
The MAGP wave function was implemented as part of a PhD project in 2014 and, while it worked fine then in tests, it has seen little use since. Let us know if you encounter problems.
Best,
Pablo

 Posts: 52
 Joined: Thu Jan 30, 2014 1:25 am
Re: Multigeminal wave functions
Hi Fan,
Best,
Pablo
I'm afraid I don't.Fan_Wang wrote: Do you any example on using it?
Geminals and multigeminals remain very much untested. I would not expect to be able to get much off them though  you might be better off using some form of truncated CI expansion of a largeish size, reoptimizing its coefficients in the presence of the Jastrow factor.With CASSCFJastrow wavefunction in DMC, the result is improved, but still unsatisfactory. I would like to try some other trial wavefunction such as JAGP in DMC.
Best,
Pablo
Hey there! I am using CASINO.

 Posts: 138
 Joined: Wed Apr 15, 2015 3:14 pm
Re: Multigeminal wave functions
Hello Pablo, Fan
I've tried to start geminal WFN calculation for Be atom involving 2p orbitals in geminal construction.
As input I want to use geminals in form described in https://aip.scitation.org/doi/10.1063/1.1503773
I use ccpVDZ basis which has 14 orbitals for Be atom.
but I've got an issue
If I do not specify the g_*,* coefficient, its value will be set to 0 and optimization type to fixed, right? (This would be a useful option since fully spinunrestricted geminals can always be reduced to diagonal form and upon optimization I don`t wont to break this)
Best Vladimir.
I've tried to start geminal WFN calculation for Be atom involving 2p orbitals in geminal construction.
As input I want to use geminals in form described in https://aip.scitation.org/doi/10.1063/1.1503773
I use ccpVDZ basis which has 14 orbitals for Be atom.
Code: Select all
GEMINAL:
Geminal 1:
Parameters:
c: [ 1.d0 , fixed ]
g_2,2: [ 0.95271200 , fixed ]
g_3,3: [ 0.17381588 , fixed ]
g_4,4: [ 0.17381378 , fixed ]
g_5,5: [ 0.17378866 , fixed ]
How could I update the number of "orbitals allowed" in the input file?
ERROR : PARSE_GMAT_EL
Error while reading label g_3,3. The row index is larger than the total
number of orbitals allowed (2). Update the number of orbitals allowed in the
input file.
If I do not specify the g_*,* coefficient, its value will be set to 0 and optimization type to fixed, right? (This would be a useful option since fully spinunrestricted geminals can always be reduced to diagonal form and upon optimization I don`t wont to break this)
Brilliant idea. What active space did you choose for the ozone in CASSCF?Fan_Wang wrote: I would like to try geminal wave function for some molecules with strong multireference character.
Best Vladimir.
In Soviet Russia Casino plays you.

 Posts: 52
 Joined: Thu Jan 30, 2014 1:25 am
Re: Multigeminal wave functions
Hi Vladimir, Fan,
Regarding the use of geminals, please have a look at Pascal Bugnion's thesis, which I've placed at https://www.tcm.phy.cam.ac.uk/~pl275/do ... thesis.pdf. Besides describing the CASINO implementation, he looks at the use of geminals for the homogeneous electron gas (see chapters 5 and 6). There are interesting conclusions here; in particular, the singlegeminal wave function provides a rather small improvement to the DMC energy over using HF nodes, especially at larger system sizes, but a multigeminal wave function based on a CIdoubles expansion is much better in this regard (but note that the number of terms in it grows quickly with system size).
I should point out that for the 14electron gas considered in the thesis one can get better VMC and DMC energies with a truncated CI containing less than 400 determinants (~ 10 optimizable coefficients) than with the multigeminals. This is why I said earlier that I would expect a truncated CI to be a better option than MAGP  but of course each system is a separate story..
Regarding the use of geminals, please have a look at Pascal Bugnion's thesis, which I've placed at https://www.tcm.phy.cam.ac.uk/~pl275/do ... thesis.pdf. Besides describing the CASINO implementation, he looks at the use of geminals for the homogeneous electron gas (see chapters 5 and 6). There are interesting conclusions here; in particular, the singlegeminal wave function provides a rather small improvement to the DMC energy over using HF nodes, especially at larger system sizes, but a multigeminal wave function based on a CIdoubles expansion is much better in this regard (but note that the number of terms in it grows quickly with system size).
I should point out that for the 14electron gas considered in the thesis one can get better VMC and DMC energies with a truncated CI containing less than 400 determinants (~ 10 optimizable coefficients) than with the multigeminals. This is why I said earlier that I would expect a truncated CI to be a better option than MAGP  but of course each system is a separate story..
Ok, this is a bug. The MAGP wave function in CASINO has only been used with electron gas orbitals, and for Gaussian orbitals the basis is mistakenly trimmed to the number of electrons (as one would do for a singleSlaterdeterminant wave function). I'll submit a patch for this shortly.How could I update the number of "orbitals allowed" in the input file?
There are indeed keywords in the CASL block to control this:If I do not specify the g_*,* coefficient, its value will be set to 0 and optimization type to fixed, right? (This would be a useful option since fully spinunrestricted geminals can always be reduced to diagonal form and upon optimization I don`t wont to break this)
Code: Select all
GEMINAL:
Default g optimizability : fixed
Default c optimizability : optimizable
Geminal 1:
...
Hey there! I am using CASINO.

 Posts: 138
 Joined: Wed Apr 15, 2015 3:14 pm
Re: Multigeminal wave functions
Hello Pablo.Pablo_Lopez_Rios wrote:Hi Vladimir
Ok, this is a bug. The MAGP wave function in CASINO has only been used with electron gas orbitals, and for Gaussian orbitals the basis is mistakenly trimmed to the number of electrons (as one would do for a singleSlaterdeterminant wave function). I'll submit a patch for this shortly.How could I update the number of "orbitals allowed" in the input file?
Yes, thanks, it will be interesting to check by generating input data in the QCHEM program as described in https://www.qchem.com/qchemwebsite/ma ... t0042.html
I will attach the corresponding example after bugfix.
Vladimir.
In Soviet Russia Casino plays you.

 Posts: 52
 Joined: Thu Jan 30, 2014 1:25 am
Re: Multigeminal wave functions
Hi Vladimir, Fan,
I've just submitted a patch to enable geminal support for gaussian/planewave/blip orbitals. It was quite a bit more work than I anticipated, with the geminal.f90 module requiring a number of bugfixes.
There is a new autotest example under examples/TEST/Input/be_geminal/opt (based on Vladimir's example) whose parameters.casl file you might want to use as template/reference for your calculations when the patch lands.
Best,
Pablo
I've just submitted a patch to enable geminal support for gaussian/planewave/blip orbitals. It was quite a bit more work than I anticipated, with the geminal.f90 module requiring a number of bugfixes.
There is a new autotest example under examples/TEST/Input/be_geminal/opt (based on Vladimir's example) whose parameters.casl file you might want to use as template/reference for your calculations when the patch lands.
Best,
Pablo
Hey there! I am using CASINO.
Re: Multigeminal wave functions
Thank you very much for your effort. I will try it.
with best regards,
Fan
with best regards,
Fan
Pablo_Lopez_Rios wrote:Hi Vladimir, Fan,
I've just submitted a patch to enable geminal support for gaussian/planewave/blip orbitals. It was quite a bit more work than I anticipated, with the geminal.f90 module requiring a number of bugfixes.
There is a new autotest example under examples/TEST/Input/be_geminal/opt (based on Vladimir's example) whose parameters.casl file you might want to use as template/reference for your calculations when the patch lands.
Best,
Pablo

 Posts: 52
 Joined: Thu Jan 30, 2014 1:25 am
Re: Multigeminal wave functions
Patch now available in current beta.
Best,
Pablo
Best,
Pablo
Hey there! I am using CASINO.