Random failures with pFON

Questions
#1

I am trying to use pFON. I ran the sample provided in the manual. The input file looks like this:

type or paste c$molecule
0 1
Pt -0.20408 1.19210 0.54029
Pt 2.61132 1.04687 0.66196
Pt 0.83227 0.03296 -1.49084
Pt 0.95832 -1.05360 0.92253
Pt -1.66760 -1.07875 -1.02416
$end
$rem
METHOD pbe
MAX_SCF_CYCLES 200
ECP fit-lanl2dz
BASIS lanl2dz
OCCUPATIONS 2 ! pseudo-fractional occupation numbers
FON_NORB 10 ! 10 fractionally occupied orbitals above and below the Fermi level
FON_T_START 1000 ! starting electronic temperature: 1000 K
FON_T_END 0 ! final electronic temperature: 0 K
FON_T_METHOD 2 ! constant cooling scheme
FON_T_SCALE 25 ! reduce the temperature by 25 K per cooling step
FON_E_THRESH 5 ! freeze occupation numbers once DIIS error is 10-5
GEN_SCFMAN false
INTEGRAL_SYMMETRY false
$end

I have run that input 4 times. The first time it ran to an apparent completion. The ouput looks like this (truncated so the forum software doesn’t object):


Running Job 1 of 1 pFON_test.inp
qchem pFON_test.inp_3027445.0 /work/qcscratch/pFON_test/ 1
/work/QChem6p3/exe/qcprog.exe_s pFON_test.inp_3027445.0 /work/qcscratch/pFON_test/
                  Welcome to Q-Chem
     A Quantum Leap Into The Future Of Chemistry


 Q-Chem 6.3, Q-Chem, Inc., Pleasanton, CA (2025)

 Q-Chem 6.3.0 for Intel X86 EM64T Linux

 Q-Chem begins on Wed Jun 18 17:03:50 2025  

 Host: 
0

     Scratch files written to /work/qcscratch/pFON_test//
 May2125 |scratch|qcdevops|jenkins|workspace|build_RNUM -1
 Processing $rem in /work/QChem6p3/config/preferences:
 Processing $rem in /root/.qchemrc:

	 WARNING: BrianQC module will not be invoked for the SCF part
	 as one of the requested features requires GEN_SCFMAN = FALSE.

 Checking the input file for inconsistencies... 	...done.
 Reading auxiliary files from /work/QChem6p3/qcaux (QCAUX)

--------------------------------------------------------------
User input:
--------------------------------------------------------------
$molecule
0 1
Pt -0.20408 1.19210 0.54029
Pt 2.61132 1.04687 0.66196
Pt 0.83227 0.03296 -1.49084
Pt 0.95832 -1.05360 0.92253
Pt -1.66760 -1.07875 -1.02416
$end
$rem
METHOD pbe
MAX_SCF_CYCLES 200
ECP fit-lanl2dz
BASIS lanl2dz
OCCUPATIONS 2 ! pseudo-fractional occupation numbers
FON_NORB 10 ! 10 fractionally occupied orbitals above and below the Fermi level
FON_T_START 1000 ! starting electronic temperature: 1000 K
FON_T_END 0 ! final electronic temperature: 0 K
FON_T_METHOD 2 ! constant cooling scheme
FON_T_SCALE 25 ! reduce the temperature by 25 K per cooling step
FON_E_THRESH 5 ! freeze occupation numbers once DIIS error is 10-5
GEN_SCFMAN false
INTEGRAL_SYMMETRY false
$end
--------------------------------------------------------------
 ----------------------------------------------------------------
             Standard Nuclear Orientation (Angstroms)
    I     Atom           X                Y                Z
 ----------------------------------------------------------------
    1      Pt      0.1121089483     0.0451596959     1.4924250209
    2      Pt      2.4420033904     0.2156964253    -0.0902567584
    3      Pt     -0.2792551127     1.2077465167    -0.7522001137
    4      Pt      0.3392477943    -1.3657719210    -0.6284544158
    5      Pt     -2.6141050203    -0.1028307170    -0.0215137329
 ----------------------------------------------------------------
 Molecular Point Group                 C1    NOp =  1
 Largest Abelian Subgroup              C1    NOp =  1
 Nuclear Repulsion Energy =         584.07102997 hartrees
 There are       45 alpha and       45 beta electrons
 Requested basis set is LANL2DZ
 There are 40 shells and 110 basis functions

 Total QAlloc Memory Limit 1000000 MB
 Mega-Array Size       188 MB
 MEM_STATIC part       192 MB


                       Distance Matrix (Angstroms)
             Pt(  1)   Pt(  2)   Pt(  3)   Pt(  4)
   Pt(  2)  2.821768
   Pt(  3)  2.557952  2.971124
   Pt(  4)  2.557430  2.685569  2.649690
   Pt(  5)  3.121883  5.066598  2.775435  3.268897
 
 A cutoff of  1.0D-09 yielded    811 shell pairs
 There are      6169 function pairs (      7355 Cartesian)
 Requested basis set is LANL2DZ
 Compound shells will be simplified
 There are 40 shells and 110 basis functions
 A cutoff of  1.0D-09 yielded    811 shell pairs
 There are      6169 function pairs (      7355 Cartesian)
 Smallest overlap matrix eigenvalue = 1.92E-03

 Scale SEOQF with 1.000000e-01/1.000000e-01/1.000000e-01

 Standard Electronic Orientation quadrupole field applied
 Nucleus-field energy     =     0.0000000065 hartrees
 Guess from superposition of atomic densities
 Warning:  Energy on first SCF cycle will be non-variational
 SAD guess density has 90.000000 electrons

-------------------------------------------------
Fractional occupation number algorithm turned on.
-------------------------------------------------

Initial Temperature =   1000.000 K
Final Temperature =      0.000 K
-------------------------------------------------

 A restricted Kohn-Sham SCF calculation will be
 performed using Pulay DIIS extrapolation
 Exchange:  PBE      Correlation:  PBE
 Using SG-1 standard quadrature grid
 SCF converges when DIIS error is below 1.0E-05
 using 30 threads for integral computing
 -------------------------------------------------------
 OpenMP Integral computing Module                
 Release: version 1.0, May 2013, Q-Chem Inc. Pittsburgh 
 -------------------------------------------------------

---- Fractional Occupation Number Information ----
Temperature =   1000.000 K
Fermi level =  -0.165532 Hartree
HOMO-LUMO gap =   0.002784 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   2.66e-02
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

 ---------------------------------------
  Cycle       Energy         DIIS Error
 ---------------------------------------
    1    -596.0997274798      2.66E-02

---- Fractional Occupation Number Information ----
Temperature =    975.000 K
Fermi level =  -0.110959 Hartree
HOMO-LUMO gap =   0.010281 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   9.26e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

    2    -595.5298468261      9.26E-03

---- Fractional Occupation Number Information ----
Temperature =    950.000 K
Fermi level =  -0.153529 Hartree
HOMO-LUMO gap =   0.006869 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   5.99e-02
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

    3    -577.5343070137      5.99E-02

---- Fractional Occupation Number Information ----
Temperature =    925.000 K
Fermi level =  -0.242013 Hartree
HOMO-LUMO gap =   0.005797 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   5.44e-02
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

    4    -584.5579769609      5.44E-02

---- Fractional Occupation Number Information ----
Temperature =    900.000 K
Fermi level =  -0.171867 Hartree
HOMO-LUMO gap =   0.001879 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   1.10e-02
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

    5    -595.4649702712      1.10E-02
-----
truncated
-----
   90    -595.6554025938      6.50E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.188138 Hartree
HOMO-LUMO gap =   0.002842 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.56e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   91    -595.6534187216      6.56E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.188062 Hartree
HOMO-LUMO gap =   0.003925 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.48e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   92    -595.6563446419      6.48E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.188249 Hartree
HOMO-LUMO gap =   0.003845 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.62e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   93    -595.6522885618      6.62E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.188274 Hartree
HOMO-LUMO gap =   0.004309 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.63e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   94    -595.6520583744      6.63E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.188271 Hartree
HOMO-LUMO gap =   0.003781 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.72e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   95    -595.6495738685      6.72E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.188275 Hartree
HOMO-LUMO gap =   0.002695 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.54e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   96    -595.6546902109      6.54E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.187407 Hartree
HOMO-LUMO gap =   0.002783 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.31e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   97    -595.6622976023      6.31E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.187870 Hartree
HOMO-LUMO gap =   0.002801 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.91e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   98    -595.6332978143      6.91E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.187294 Hartree
HOMO-LUMO gap =   0.001155 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   6.72e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

   99    -595.6414227856      6.72E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.190307 Hartree
HOMO-LUMO gap =   0.003739 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   5.62e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

  100    -595.6770191962      5.62E-03

  139    -595.7703033642      1.35E-05

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.187785 Hartree
HOMO-LUMO gap =   0.000156 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   1.46e-05
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

  140    -595.7703023066      1.46E-05

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.187784 Hartree
HOMO-LUMO gap =   0.000156 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   3.43e-06
thresh =   1.00e-05
---- Fractional Occupation Number Information End ----

  141    -595.7703033194      3.43E-06 Convergence criterion met
 ---------------------------------------
 SCF time:  CPU 164.42 s  wall 5.50 s
 SCF   energy =  -595.77030332
 Total energy =  -595.77030332
 
 --------------------------------------------------------------
 
                    Orbital Energies (a.u.)
 --------------------------------------------------------------
 
 Alpha MOs
 -- Occupied --
 -3.7892  -3.7885  -3.7865  -3.7673  -3.7536  -2.0577  -2.0487  -2.0459
 -2.0453  -2.0412  -2.0405  -2.0352  -2.0326  -2.0298  -2.0292  -2.0166
 -2.0165  -2.0134  -2.0036  -1.9987  -0.3853  -0.3350  -0.3140  -0.3048
 -0.3037  -0.2861  -0.2786  -0.2750  -0.2720  -0.2672  -0.2321  -0.2255
 -0.2224  -0.2206  -0.2188  -0.2166  -0.2160  -0.2118  -0.2085  -0.2047
 -0.2027  -0.1993  -0.1978  -0.1914  -0.1879
 -- Virtual --
 -0.1877  -0.1862  -0.1531  -0.1518  -0.1300  -0.0468  -0.0351  -0.0313
 -0.0294  -0.0233  -0.0199   0.0227   0.0240   0.0362   0.0417   0.0431
  0.0445   0.0642   0.0709   0.0745   0.0763   0.0999   0.1023   0.1030
  0.1061   0.1088   0.1509   0.1523   0.1966   0.2210   0.2268   0.2446
  0.2818   0.3075   0.3162   0.3268   0.3294   0.3440   0.3798   0.3825
  0.4380   0.4432   0.4514   0.4595   0.4716   0.4754   0.4809   0.5169
  0.5204   0.5277   0.5375   0.5620   0.5685   0.5757   0.6053   0.6254
  0.6417   0.6497   0.6612   0.6671   3.8225   5.2580   5.6371   6.7849
  7.3361
 --------------------------------------------------------------
 
          Ground-State Mulliken Net Atomic Charges

     Atom                 Charge (a.u.)
  ----------------------------------------
      1 Pt                    0.062831
      2 Pt                   -0.059849
      3 Pt                    0.046017
      4 Pt                    0.067138
      5 Pt                   -0.116138
  ----------------------------------------
  Sum of atomic charges =     0.000000

 -----------------------------------------------------------------
                    Cartesian Multipole Moments
 -----------------------------------------------------------------
    Charge (ESU x 10^10)
                -0.0000
    Dipole Moment (Debye)
         X       0.6588      Y      -0.1871      Z       0.0786
       Tot       0.6894
    Quadrupole Moments (Debye-Ang)
        XX    -117.3472     XY       1.8136     YY    -112.0469
        XZ      -0.5237     YZ      -0.0339     ZZ    -112.1663
    Octopole Moments (Debye-Ang^2)
       XXX       4.0997    XXY      -0.2560    XYY       1.6592
       YYY      -3.8152    XXZ      -0.5034    XYZ       2.8013
       YYZ      -9.7236    XZZ       1.4077    YZZ       0.9022
       ZZZ      10.9915
    Hexadecapole Moments (Debye-Ang^3)
      XXXX   -1916.1394   XXXY      49.0727   XXYY    -441.9946
      XYYY      -6.5485   YYYY    -584.5757   XXXZ     -12.5558
      XXYZ      -2.3480   XYYZ       0.3526   YYYZ       2.5706
      XXZZ    -444.7633   XYZZ      -3.5306   YYZZ    -189.4255
      XZZZ       1.5728   YZZZ      -0.3284   ZZZZ    -554.3558
 -----------------------------------------------------------------
 Total job time:  5.68s(wall), 167.92s(cpu) 
 Wed Jun 18 17:03:56 2025

        *************************************************************
        *                                                           *
        *  Thank you very much for using Q-Chem.  Have a nice day.  *
        *                                                           *
        *************************************************************

I ran it again, 3 more times, and it fails, the SCF does not converge. The failure is different in every run.

This is the output from the final run:


Running Job 1 of 1 pFON_test.inp
qchem pFON_test.inp_3029317.0 /work/qcscratch/pFON_test/ 1
/work/QChem6p3/exe/qcprog.exe_s pFON_test.inp_3029317.0 /work/qcscratch/pFON_test/
                  Welcome to Q-Chem
     A Quantum Leap Into The Future Of Chemistry


 Q-Chem 6.3, Q-Chem, Inc., Pleasanton, CA (2025)

 E. Epifanovsky,  A. T. B. Gilbert,  Xintian Feng,  Joonho Lee,  Yuezhi Mao,  
 N. Mardirossian,  P. Pokhilko,  A. White,  M. Wormit,  M. P. Coons,  
 A. L. Dempwolff,  Zhengting Gan,  D. Hait,  P. R. Horn,  L. D. Jacobson,  
 I. Kaliman,  J. Kussmann,  A. W. Lange,  Ka Un Lao,  D. S. Levine,  Jie Liu,  
 S. C. McKenzie,  A. F. Morrison,  K. D. Nanda,  F. Plasser,  D. R. Rehn,  
 M. L. Vidal,  Zhi-Qiang You,  Ying Zhu,  Huseyin Aksu,  B. Alam,  
 B. Albrecht,  A. Aldossary,  E. Alguire,  J. H. Andersen,  
 J. E. Arias-Martinez,  V. Athavale,  F. Ballesteros,  D. Barton,  K. Begam,  
 A. Behn,  N. Bellonzi,  Y. A. Bernard,  E. J. Berquist,  H. Burton,  
 S. Camps,  A. Carreras,  K. Carter-Fenk,  Mathew Chow,  Romit Chakraborty,  
 Chandrima Chakravarty,  Junhan Chen,  A. D. Chien,  K. D. Closser,  
 V. Cofer-Shabica,  L. Cunha,  S. Dasgupta,  Jia Deng,  Joseph Dickinson,  
 M. de Wergifosse,  M. Diedenhofen,  L. B. Dittmer,  Hainam Do,  Wenjie Dou,  
 S. Ehlert,  Po-Tung Fang,  S. Fatehi,  Qingguo Feng,  Jonathan Fetherolf,  
 T. Friedhoff,  Thomas Froitzheim,  Sarai Folkestad,  B. Ganoe,  J. Gayvert,  
 Qinghui Ge,  G. Gidofalvi,  M. Gimferrer,  G. Giudetti,  M. Goldey,  
 Montgomery Gray,  J. Gomes,  C. Gonzalez-Espinoza,  S. Gulania,  A. Gunina,  
 J. A. Gyamfi,  M. W. D. Hanson-Heine,  P. H. P. Harbach,  A. W. Hauser,  
 M. F. Herbst,  M. Hernandez Vera,  M. Hodecker,  Z. C. Holden,  S. Houck,  
 Xunkun Huang,  Kerwin Hui,  B. C. Huynh,  K. Ikeda,  M. Ivanov,  
 Nayanthara K. Jayadev,  Hyunjun Ji,  Zuxin Jin,  Hanjie Jiang,  
 Subrata Jana,  B. Kaduk,  S. Kaehler,  R. Kang,  Richard Kang,  
 K. Khistyaev,  Jaehoon Kim,  Yongbin Kim,  P. Klunzinger,  Z. Koczor-Benda,  
 Joong Hoon Koh,  D. Kosenkov,  Saikiran Kotaru,  L. Koulias,  T. Kowalczyk,  
 C. M. Krauter,  K. Kue,  A. Kunitsa,  T. Kus,  A. Landau,  C. W. Lander,  
 K. V. Lawler,  D. Lefrancois,  S. Lehtola,  Rain Li,  Shaozhi Li,  
 Tao E. Li,  Yi-Pei Li,  Jiashu Liang,  M. Liebenthal,  Hung-Hsuan Lin,  
 You-Sheng Lin,  Fenglai Liu,  Kuan-Yu Liu,  Xiao Liu,  M. Loipersberger,  
 A. Luenser,  C. Malbon,  Aniket Mandal,  Manisha,  A. Manjanath,  
 P. Manohar,  E. Mansoor,  S. F. Manzer,  Shan-Ping Mao,  A. V. Marenich,  
 T. Markovich,  S. Mason,  F. Matz,  S. A. Maurer,  Samuel May,  
 Alexandra McIsaac,  P. F. McLaughlin,  M. F. S. J. Menger,  J.-M. Mewes,  
 S. A. Mewes,  R. E. Moorby,  P. Morgante,  Mohammad Mostafanejad,  
 Madhubani Mukherjee,  J. W. Mullinax,  Quyen Nguyen,  Avik Kumar Ojha,  
 K. J. Oosterbaan,  Eno Paenurk,  Xiaoliang Pan,  G. Paran,  V. Parravicini,  
 R. L. Patterson,  Alexander C. Paul,  Suranjan K. Paul,  F. Pavosevic,  
 Zheng Pei,  P. Pokhilko,  S. Prager,  E. I. Proynov,  E. Ramos,  B. Rana,  
 A. E. Rask,  A. Rettig,  R. M. Richard,  F. Rob,  E. Rossomme,  S. Roy,  
 T. Scheele,  M. Scheurer,  M. Schneider,  P. E. Schneider,  Tim K. Schramm,  
 N. Sergueev,  S. M. Sharada,  Hengyuan Shen,  W. Skomorowski,  D. W. Small,  
 C. J. Stein,  Alistair J. Sterling,  Yingli Su,  Yu-Chuan Su,  
 E. J. Sundstrom,  J. Talbot,  J. A. Tan,  Zhen Tao,  Hung-Hsuan Teh,  
 J. Thirman,  C. Titeca,  N. Tkachenko,  Hung-Yi Tsai,  T. Tsuchimochi,  
 N. M. Tubman,  C. Utku,  S. P. Veccham,  O. Vydrov,  Z. Wang,  Rahel Weiss,  
 J. Wenzel,  Jonathan Wong,  J. Witte,  H. Wu,  Yanze Wu,  A. Yamada,  
 Chou-Hsun Yang,  Kun Yao,  S. Yeganeh,  S. R. Yost,  Qi Yu,  A. Zech,  
 F. Zeller,  Chongxiao Zhao,  T. Zhao,  Igor Ying Zhang,  Xing Zhang,  
 Yu Zhang,  D. Zuev,  A. Aspuru-Guzik,  A. T. Bell,  N. A. Besley,  
 K. B. Bravaya,  B. R. Brooks,  D. Casanova,  Jeng-Da Chai,  Hsing-Ta Chen,  
 S. Coriani,  C. J. Cramer,  A. E. DePrince, III,  R. A. DiStasio Jr.,  
 A. Dreuw,  B. D. Dunietz,  T. R. Furlani,  W. A. Goddard III,  S. Grimme,  
 S. Hammes-Schiffer,  T. Head-Gordon,  W. J. Hehre,  Chao-Ping Hsu,  
 T.-C. Jagau,  Yousung Jung,  A. Klamt,  Jing Kong,  D. S. Lambrecht,  
 Xiangyuan Li,  WanZhen Liang,  N. J. Mayhall,  C. W. McCurdy,  J. B. Neaton,  
 T. Neudecker,  C. Ochsenfeld,  J. A. Parkhill,  R. Peverati,  
 V. A. Rassolov,  Haisheng Ren,  Yihan Shao,  L. V. Slipchenko,  
 R. P. Steele,  J. E. Subotnik,  A. J. W. Thom,  A. Tkatchenko,  
 D. G. Truhlar,  T. Van Voorhis,  Fan Wang,  T. A. Wesolowski,  K. B. Whaley,  
 H. L. Woodcock III,  P. M. Zimmerman,  S. Faraji,  P. M. W. Gill,  
 M. Head-Gordon,  J. M. Herbert,  A. I. Krylov

 Contributors to earlier versions of Q-Chem not listed above: 
 R. D. Adamson,  B. Austin,  R. Baer,  J. Baker,  G. J. O. Beran,  
 K. Brandhorst,  S. T. Brown,  E. F. C. Byrd,  Arup K. Chakraborty,  
 G. K. L. Chan,  Chun-Min Chang,  Yunqing Chen,  C.-L. Cheng,  
 Siu Hung Chien,  D. M. Chipman,  D. L. Crittenden,  H. Dachsel,  
 R. J. Doerksen,  A. D. Dutoi,  R. G. Edgar,  J. Fosso-Tande,  
 L. Fusti-Molnar,  D. Ghosh,  A. Ghysels,  A. Golubeva-Zadorozhnaya,  
 J. Gonthier,  M. S. Gordon,  S. R. Gwaltney,  G. Hawkins,  J. E. Herr,  
 A. Heyden,  S. Hirata,  E. G. Hohenstein,  G. Kedziora,  F. J. Keil,  
 C. Kelley,  Jihan Kim,  R. A. King,  R. Z. Khaliullin,  P. P. Korambath,  
 W. Kurlancheek,  A. Laurent,  A. M. Lee,  M. S. Lee,  S. V. Levchenko,  
 Ching Yeh Lin,  D. Liotard,  E. Livshits,  R. C. Lochan,  I. Lotan,  
 L. A. Martinez-Martinez,  P. E. Maslen,  N. Nair,  D. P. O'Neill,  
 D. Neuhauser,  E. Neuscamman,  C. M. Oana,  R. Olivares-Amaya,  R. Olson,  
 T. M. Perrine,  B. Peters,  P. A. Pieniazek,  A. Prociuk,  Y. M. Rhee,  
 J. Ritchie,  M. A. Rohrdanz,  E. Rosta,  N. J. Russ,  H. F. Schaefer III,  
 M. W. Schmidt,  N. E. Schultz,  S. Sharma,  N. Shenvi,  C. D. Sherrill,  
 A. C. Simmonett,  A. Sodt,  T. Stein,  D. Stuck,  K. S. Thanthiriwatte,  
 V. Vanovschi,  L. Vogt,  Tao Wang,  A. Warshel,  M. A. Watson,  
 C. F. Williams,  Q. Wu,  X. Xu,  Jun Yang,  W. Zhang,  Yan Zhao

   Please cite Q-Chem as follows:
  "Software for the frontiers of quantum chemistry:
   An overview of developments in the Q-Chem 5 package"
   J. Chem. Phys. 155, 084801 (2021)
   https://doi.org/10.1063/5.0055522 (open access)

 Q-Chem 6.3.0 for Intel X86 EM64T Linux

 Parts of Q-Chem use Armadillo 12.8.2 (Cortisol Injector).
 http://arma.sourceforge.net/

 Q-Chem begins on Wed Jun 18 17:43:13 2025  

 Host: 
0

     Scratch files written to /work/qcscratch/pFON_test//
 May2125 |scratch|qcdevops|jenkins|workspace|build_RNUM -1
 Processing $rem in /work/QChem6p3/config/preferences:
 Processing $rem in /root/.qchemrc:

	 WARNING: BrianQC module will not be invoked for the SCF part
	 as one of the requested features requires GEN_SCFMAN = FALSE.

 Checking the input file for inconsistencies... 	...done.
 Reading auxiliary files from /work/QChem6p3/qcaux (QCAUX)

--------------------------------------------------------------
User input:
--------------------------------------------------------------
$molecule
0 1
Pt -0.20408 1.19210 0.54029
Pt 2.61132 1.04687 0.66196
Pt 0.83227 0.03296 -1.49084
Pt 0.95832 -1.05360 0.92253
Pt -1.66760 -1.07875 -1.02416
$end
$rem
METHOD pbe
MAX_SCF_CYCLES 200
ECP fit-lanl2dz
BASIS lanl2dz
OCCUPATIONS 2 ! pseudo-fractional occupation numbers
FON_NORB 10 ! 10 fractionally occupied orbitals above and below the Fermi level
FON_T_START 1000 ! starting electronic temperature: 1000 K
FON_T_END 0 ! final electronic temperature: 0 K
FON_T_METHOD 2 ! constant cooling scheme
FON_T_SCALE 25 ! reduce the temperature by 25 K per cooling step
FON_E_THRESH 5 ! freeze occupation numbers once DIIS error is 10-5
GEN_SCFMAN false
INTEGRAL_SYMMETRY false
$end
--------------------------------------------------------------
 ----------------------------------------------------------------
             Standard Nuclear Orientation (Angstroms)
    I     Atom           X                Y                Z
 ----------------------------------------------------------------
    1      Pt      0.1121089483     0.0451596959     1.4924250209
    2      Pt      2.4420033904     0.2156964253    -0.0902567584
    3      Pt     -0.2792551127     1.2077465167    -0.7522001137
    4      Pt      0.3392477943    -1.3657719210    -0.6284544158
    5      Pt     -2.6141050203    -0.1028307170    -0.0215137329
 ----------------------------------------------------------------
 Molecular Point Group                 C1    NOp =  1
 Largest Abelian Subgroup              C1    NOp =  1
 Nuclear Repulsion Energy =         584.07102997 hartrees
 There are       45 alpha and       45 beta electrons
 Requested basis set is LANL2DZ
 There are 40 shells and 110 basis functions

 Total QAlloc Memory Limit 1000000 MB
 Mega-Array Size       188 MB
 MEM_STATIC part       192 MB


                       Distance Matrix (Angstroms)
             Pt(  1)   Pt(  2)   Pt(  3)   Pt(  4)
   Pt(  2)  2.821768
   Pt(  3)  2.557952  2.971124
   Pt(  4)  2.557430  2.685569  2.649690
   Pt(  5)  3.121883  5.066598  2.775435  3.268897
 
 A cutoff of  1.0D-09 yielded    811 shell pairs
 There are      6169 function pairs (      7355 Cartesian)
 Requested basis set is LANL2DZ
 Compound shells will be simplified
 There are 40 shells and 110 basis functions
 A cutoff of  1.0D-09 yielded    811 shell pairs
 There are      6169 function pairs (      7355 Cartesian)
 Smallest overlap matrix eigenvalue = 1.92E-03

 Scale SEOQF with 1.000000e-01/1.000000e-01/1.000000e-01

 Standard Electronic Orientation quadrupole field applied
 Nucleus-field energy     =     0.0000000065 hartrees
 Guess from superposition of atomic densities
 Warning:  Energy on first SCF cycle will be non-variational
 SAD guess density has 90.000000 electrons

-------------------------------------------------
Fractional occupation number algorithm turned on.
-------------------------------------------------

Initial Temperature =   1000.000 K
Final Temperature =      0.000 K
-------------------------------------------------

 A restricted Kohn-Sham SCF calculation will be
 performed using Pulay DIIS extrapolation
 Exchange:  PBE      Correlation:  PBE
 Using SG-1 standard quadrature grid
 SCF converges when DIIS error is below 1.0E-05
 using 30 threads for integral computing
 -------------------------------------------------------
 OpenMP Integral computing Module                
 Release: version 1.0, May 2013, Q-Chem Inc. Pittsburgh 
 -------------------------------------------------------

---- Fractional Occupation Number Information ----
Temperature =   1000.000 K
Fermi level =  -0.165532 Hartree
HOMO-LUMO gap =   0.002784 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   2.66e-02
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

 ---------------------------------------
  Cycle       Energy         DIIS Error
 ---------------------------------------
    1    -596.0997274798      2.66E-02
------
truncated
------
  199    -595.7540994741      2.36E-03

---- Fractional Occupation Number Information ----
Temperature =     25.000 K
Fermi level =  -0.189001 Hartree
HOMO-LUMO gap =   0.004548 Hartree
Number of active orbitals = 20
Number of active electrons = 10
EMax =   5.54e-03
thresh =   1.00e-05
Generating Pseudo-Fermi distribution of occupation numbers.
--
# Rescaled active electrons =     10.000
Writing occupation numbers to disk ...
---- Fractional Occupation Number Information End ----

  200    -595.6970421624      5.54E-03    Convergence failure

 Q-Chem fatal error occurred in module scfman/scfman.C, line 5636:

 SCF failed to converge


 Please submit a crash report at q-chem.com/reporter

Any idea why it failed after the first success?

#2

This is unusual but not unprecedented in my experience. Your first job, in a sense, barely converged, you might say you got lucky and after 140 cycles the DIIS error just happened to wander beneath the convergence criterion while in the subsequent jobs you weren’t so lucky. This can happen due to small differences in the integrals because multithreading operations aren’t precisely defined until runtime, at least that’s my (limited) understanding based on some reading that I did when my group encountered this years ago, in that case on hematite (Fe2O3) cluster models.

The solution here is to find a convergence algorithm that works. I might first suggest tightening up THRESH (because I always suggest that at the first sign of trouble, say, THRESH = 12), but then try different versions of SCF_GUESS and SCF_ALGORITHM to see if you can find something that converges more directly.

#3

Thanks John. I tried your suggestions.

I tried THRESH=12, 14, 20 and still could not get e repeatable result.

For THRESH=20

I tried SCF_ALGORITHM=GDM and got nan results for energy and convergence criteria.

I tried SCF_ALGORITHM=GDM and could not get repeatable results.

This appears it might be a problem with an uninitialized variable being used in the Fermi Level calculations.

I have no idea how to proceed with using pFON.

#4

What happens if you try a different SCF_GUESS?

By the way, the tightest meaningful value of THRESH is 15, or possibly 16, since double precision corresponds to about 15.5 decimal digits.

#5

Sorry. I erred in my post.

I tried SCF_GUESS=GWH, not SCF_ALGORITHM

#6

This is a GGA functional and the HOMO/LUMO gap is extremely small - it’s a difficult convergence problem by definition. (The gap is printed out for pFON, by the way.) I found that I can get it to converge in 67 cycles using SCF_GUESS = AUTOSAD, which is often a good choice in case of trouble. If that doesn’t work for other similar small-gap systems, you might need to adjust the temperature program for pFON.

UPDATE: Another approach that will work is to converge PBE0 orbitals first (as the hybrid will open up the gap) and then use those as a guess if you really want the GGA orbitals.

$molecule
0 1
Pt -0.20408 1.19210 0.54029
Pt 2.61132 1.04687 0.66196
Pt 0.83227 0.03296 -1.49084
Pt 0.95832 -1.05360 0.92253
Pt -1.66760 -1.07875 -1.02416
$end

$rem
METHOD pbe0
MAX_SCF_CYCLES 100
ECP fit-lanl2dz
BASIS lanl2dz
thresh 12
scf_guess autosad
scf_convergence 8
$end

@@@

$molecule
read
$end


$rem
scf_guess read
method pbe
MAX_SCF_CYCLES 100
ECP fit-lanl2dz
BASIS lanl2dz
thresh 12
scf_algorithm gdm
incfock false
$end
#7

Does it converge to the same result when you run the exact same job 3 times?

#8

Not quite but your temperature program doesn’t go all the way to zero so you wouldn’t expect to get exactly the same energy as a calculation without pFON.

#9

John,

Thanks for your help.

I’m not thinking about comparing a pFON calculation to a non-pFON one. My question was about multiple runs of the identical pFON input file to see if we can get repeatability. It appears, in its current implementation, that would be uncertain.

In any event, since I was using the example provided in the manual as a test method to see how pFON works, I’m not going to invest any more time.

I might suggest the pFON example in the manual be one that doesn’t require finagling and generates repeatable results.

Thanks again for your help.

#10

I’ll look into finding a new pFON example for the manual. For what it’s worth, this particular SCF can be converged using SCF_ALGORITHM = ROBUST, which is new in Q-Chem v. 6.3, rather than pFON.