backflow transformation for N2
Posted: Sun Sep 28, 2014 3:41 am
With single-determinant SJ wavefunction, error in atomization energy for N2 is about 5 Kcal/mol using LDA orbitals according to JCTC, 8, 2255 (2012). I got similar results with CASINO. I am wondering whether this error could be reduced with backflow transformation. Unfortunately, I could not get reasonable result when optimizing parameters for N2. (It seems OK with N). The initial Jastrow factors are from emin optimization without bf transformation. When I set "Apply no-curl constraint" to zero, results with emin optimization will have very large variance, much larger than that without bf transformation. When this parameter is set to 1, it seems to me the backflow transformation does not work at all ( the parameters in bf part are smaller than 1E-5 and the resulting energy does not change at all.) Is there anything wrong with my setting for bf part or input?
in correlation.data file:
in input file:
in correlation.data file:
Code: Select all
START BACKFLOW
Title
AE Nitrogen
Truncation order
3
START ETA TERM
Expansion order
8
Spin dep (0->uu=dd=ud; 1->uu=dd/=ud; 2->uu/=dd/=ud)
1
Cut-off radii ; Optimizable (0=NO; 1=YES; 2=YES BUT NO SPIN-DEP)
0.831243458551654 1 ! L_1
Parameter ; Optimizable (0=NO; 1=YES)
END ETA TERM
START MU TERM
Number of sets
1
START SET 1
Number of atoms in set
2
Labels of the atoms in this set
1 2
Type of e-N cusp conditions (0->PP/cuspless AE; 1->AE with cusp)
1
Expansion order
6
Spin dep (0->u=d; 1->u/=d)
0
Cutoff (a.u.) ; Optimizable (0=NO; 1=YES)
3.68216019293890 1
Parameter values ; Optimizable (0=NO; 1=YES)
END SET 1
END MU TERM
START PHI TERM
Number of sets
1
START SET 1
Number of atoms in set
2
Labels of the atoms in this set
1 2
Type of e-N cusp conditions (0=PP; 1=AE)
1
Apply no-curl constraint (0=NO; 1=YES)
0
Electron-nucleus expansion order N_eN
3
Electron-electron expansion order N_ee
3
Spin dep (0->uu=dd=ud; 1->uu=dd/=ud; 2->uu/=dd/=ud)
0
Cutoff (a.u.) ; Optimizable (0=NO; 1=YES)
3.59996205053959 1
Parameter values ; Optimizable (0=NO; 1=YES)
END SET 1
END PHI TERM
END BACKFLOW
Code: Select all
vmc_equil_nstep : 5000 #*! Number of equilibration steps (Integer)
vmc_nstep : 2000000 #*! Number of steps (Integer)
vmc_nblock : 10 #*! Number of checkpoints (Integer)
vmc_nconfig_write : 20000 #*! Number of configs to write (Integer)
opt_method : emin #*! Opt method (varmin/madmin/emin/...)
opt_cycles : 10 #*! Number of optimization cycles (Integer)
opt_jastrow : T #*! Optimize Jastrow factor (Boolean)
opt_det_coeff : F #*! Optimize determinant coeffs (Boolean)
opt_backflow : T #*! Optimize backflow parameters (Boolean)
opt_orbitals : F #*! Optimize orbital parameters (Boolean)