[CP2K-user] [CP2K:21462] Re: Regarding the problem of using three functionals to optimize the spatial structure of the high spin state of the spin crossover material [Fe(pz)][Ni(CN)4]

[Daniel Lee]

 the names of the corresponding attachment file are
attachment 1: h.pw.vr_d.so2_PBED2_e-5f-4c-10_em10_w10r110_mb7_ps0pc1_k4.in 
attachment 2: l.pw.vr_d.so2_PBED2_e-5f-4c-10_em10_w10r110_mb7_ps0pc1_k4.in 
attachment 3: QEB3LYP_h output
attachment 4: l_tpssh_2_t2mhg_ed12es6_d3f4_ps0pc1.inp 
attachment 5: l_m06l_t2mmg_gm_k6_ed12es6_d3f4_ps3pc1.inp 
attachment 6: h_b3lyp_2_tmhg_ed12eg12_es6.inp 
attachment 7: h_tpssh_2_t2mhg_ed12es5_d3f4_ps0pc1.inp
attachment 8: h_m06l_t2mmg_gm_k6_ed12es6_d3f4_ps0pc1.inp 
attachment 9: h_m06l_t2mmg_gm_k6_ed12es6_d3f4_ps0pc1.out
attachment 10: h_pbe-d3bj_tmpg_gp_k6_ed12es6_d3f4.inp 
attachment 11: h_pbe-d3bj_2_tmpg_gp_cd_ed12es6_d3f4.inp 
attachment 12: h_pbe-d3bj_2_tmpg_gp_cd_ed12es6_d3f4.out


On Tuesday, May 13, 2025 at 11:30:19 AM UTC+8 Daniel Lee wrote:

> Hi, greetings:
>
> I hope to use CP2K to optimize the spatial structure of the high spin 
> state of the spin crossover periodic crystal [Fe(pyrazine)][Ni(CN)4] (a MOF 
> type material, the crystal structure is shown in Figure 1 
> <https://imgur.com/a/2xhQjKi>).
>
> This material is in a low spin state at normal pressure and low 
> temperature, which is a diamagnetic state. The d-layer electronic 
> configuration of Fe(ii) is t2g6, spin is 0, and Ni spin is 0. It will 
> automatically transform into a high spin state at normal pressure and 300K, 
> which is a paramagnetic state, the d-layer electronic configuration of 
> Fe(ii) becomes t2g4eg2, spin is 2, and Ni spin is 0; the difference between 
> the high and low spin states in the spatial structure is mainly reflected 
> in the different bond lengths of the Fe-N octahedron (high---2.1+A, 
> low---1.9+A), and the bond lengths of other chemical bonds remain basically 
> unchanged. The unit cell of this material has 20 atoms.
>
> There are several studies in the field of spin crossover research (such as 
> a recent one DOI: 10.1063/5.0157187) showing that tpssh, b3lyp and m06l are 
> three functionals that are fairly good at describing the properties of spin 
> crossover materials, so I would like to use these three functionals to 
> optimize the spatial structure of the high and low spin states of 
> [Fe(pyrazine)][Ni(CN)4] and compare the simulation results of different 
> functionals.
>
> Recently, a study (10.1021/acs.jpcc.2c01030) used quantum espresso to 
> simulate the PBE+D2 calculation of a similar material 
> [Fe(pyrazine)][Pt(CN)4]. Therefore, I used the method of this study to 
> optimize the spatial structure of the high and low spin states of 
> [Fe(pyrazine)][Ni(CN)4] using QE's PBE+D2. After setting different spin 
> polarization parameters for the input files corresponding to the high and 
> low spin state according to the experimental data (see attachment 1 for the 
> high spin input file and attachment 2 for the low spin input file), the 
> vc-relax calculations converged successfully, and the results also 
> reflected the spatial structure and magnetic properties of the high and low 
> spin states. The calculated bond length data was in line with expectations 
> (see Figure 2 <https://imgur.com/9hMUtYb> for the optimized unit cell 
> structure for high spin state and Figure 3 <https://imgur.com/feFHAYl> 
> for low spin state).
>
> Then I tried to use tpssh, b3lyp and m06l functionals in QE to optimize 
> these spatial structures. However, for tpssh and m06l functionals, I did 
> not find a pseudopotential group that could make the optimization run 
> normally without errors (for example, the most common error is "Error in 
> routine cdiaghg (161): S matrix not positive definite"). On the other hand, 
>  although the SCF converged, the b3lyp had the problem that the calculation 
> of "Using ACE for calculation of exact exchange" would keep looping for a 
> long time on a hpc cluster(see attachment 3). Therefore, I decided to try 
> to use CP2K to simulate the three functionals of tpssh, b3lyp and m06l.
>
> I used Multiwfn to generate input files for high and low spin state 
> spatial structure optimization. The low spin state was successfully 
> simulated using three functionals: tpssh (expanding the cell to 2*2*2 and 
> only counting the Γ point, attachment 4), b3lyp (expanding the cell to 
> 2*2*2 and only counting the Γ point), and m06l (using the primitive cell, 
> with the K point of 6*6*6, attachment 5). The optimization results of the 
> two hybrid functionals t and b were in line with expectations (see Figures 
> 4 <https://imgur.com/H0NeEv1> and 5 <https://imgur.com/oYAENpH>, 
> respectively). Although the Fe-N bond length calculated by m was in the low 
> spin state range, the bond lengths that should have been equal were 
> different (see Figure 6 <https://imgur.com/Jo2x2a9>).
>
> In the high spin state simulation, although b3lyp (attachment 6) was able 
> to converge and the program successfully exited, the optimized structure 
> obtained was not ideal. Some of the 8 primitive cells in the supercell were 
> in the high spin state (Fe-N bond length was greater than 2), and some were 
> in the low spin state (Fe-N bond length was less than 2), and the Fe-N bond 
> lengths in the same primitive cell were not all equal (see Figure 7 
> <https://imgur.com/xm2jKsp>). When I used tpssh to optimize, the settings 
> I used were almost the same as those of b3lyp. However, scf did not 
> converge (it oscillated around 10E-5 in the output file), so I increased 
> EPS_SCF from 10E-6 to 10E-5 (Appendix 7) and tried the calculation again. 
> This time, SCF converged, but the forces in the geometry optimization 
> (Maximum gradient data in the output file) could not converge to the 
> default 4.5E-4 (the closest it could get was 8E-4) after running for more 
> than 12 hours. After checking the pdb file of the output geometry structure 
> change data, I found that the overall structure only had obvious changes in 
> the initial optimization stage, and no longer changed in the later stage. 
> In addition, the later structure had similar problems as the b3lyp 
> optimization result (see Figure 8 <https://imgur.com/rci6EyL>). When 
> optimizing with m06l (input attachment 8), the SCF generally oscillates 
> between 10-2 and 10-3 (output attachment 9). I tried some combinations of 
> basis vectors and pseudopotentials (https://cp2k-basis.pierrebeaujean.net/), 
> such as the basis vector and pseudopotentials for PBE and MGGA, but the SCF 
> convergence problem was not solved.
>
> I also tried to use CP2K's PBE+D3 method (using primitive cells and 6*6*6 
> K points) to optimize the high-spin state (attachment 10). After running 
> for more than 10 hours, the situation similar to tpssh high-spin state 
> simulation in which the force cannot reach the convergence limit appeared. 
> The output geometry structure change trajectory from pdb file is almost 
> stable in the later stage and the bond length and other data are consistent 
> with the high-spin state (see Figure 9 <https://imgur.com/n99RAWL>). In 
> addition, the high-spin state optimization results of PBE with 2*2*2 
> expanded cells as the initial guess of tpssh optimization also produced the 
> similar result that the force cannot reach the convergence limit in the 
> later stage and the optimized structure in the later stage has similar 
> problems as described above (see Figure 10 <https://imgur.com/Y6pIhtn>).
>
> Then I tried to use CDFT to fix the magnetic moment of Fe, but the two 
> functionals pbe and tpssh (see attachment 11) I tried faced a problem that 
> the "Target value of constraint" and "Current value of constraint" 
> polarized after the program ran for a certain period of time (see 
> attachment 12).
>
> Dear CP2K users, are there any problems in my various input file parameter 
> settings shown above? Is there any way to make the conventional DFT or CDFT 
> structure optimization results of tpssh, m06l or b3lyp successfully 
> converge to a satisfactory high spin state?
>
> Thank you very much, your help are much appreciated.
>
>                                                                                                                        
> Daniel Lee
>

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