[DFTB-Plus-User] Different trajectory and energies for different MDrestartFrequency and steps

[jsxz]

Dear Bálint,

Thank you for your reply!
I calculate the MD for CNT by using the SCC-DFTB_MPI, I got some troubles below,

When I set different steps and MDrestartFrequency (other parameters do not change), there are different trajectory and different energies.

The difference is more and more big with the MD iter increasing.  Thus the  final trajectory vary widely. I am very confused, please help me.

For example,

1) MDRestartFrequency =1,  Steps = 5000 
the trajectory:

288

MD iter: 1000

C  5.68171730   5.98251837    -12.39979513      3.90234072  -42.26408235       8.32191149      7.98495693      # position charge  velocity

C  5.43500090   5.13928932    -11.30181173      3.95051030     -4.88719190     38.22047267     -7.89803851

C  4.70000103   4.10563107    -12.05608176      3.99661671      7.50312869     8.79196619    -34.05100357

...

...

the energy:

MD step:        1000
 Pressure:                          -0.455755E-05 au    -0.134088E+09 Pa
 Potential Energy:                -489.8076912189 H       -13328.3454 eV
 MD Kinetic Energy:                  5.6509016167 H          153.7689 eV
 Total MD Energy:                 -484.1567896023 H       -13174.5766 eV
 MD Temperature:                     0.0131263684 au        4144.9744 K


2) MDRestartFrequency =10, Steps = 5000
the trajectory:

288
MD iter: 1000
    C      7.15957378      4.14567851    -11.90923109      4.29998836     32.77853952     -7.69360895      8.36132511
    C      5.84655135      4.20989546    -11.19124274      3.85657562    -19.40357398     12.82268451     -3.41764893
    C      4.97123751      3.25142449    -11.97549013      4.05333076      2.65042132    -18.48726570    -21.70284589

...

...

the energy

MD step:        1000
 Pressure:                          -0.239863E-05 au    -0.705701E+08 Pa
 Potential Energy:                -489.1187784596 H       -13309.5991 eV
 MD Kinetic Energy:                  4.9596736060 H          134.9596 eV
 Total MD Energy:                 -484.1591048536 H       -13174.6396 eV
 MD Temperature:                     0.0115207285 au        3637.9540 K

3) MDRestartFrequency =1,  Steps = 10000 

the trajectory:

288
MD iter: 1000
    C      6.76753176      5.52458542    -11.79760245      4.16939095      7.88750202     -7.30703760     -3.56225653
    C      6.67023134      4.20908088    -11.30407259      3.88162082     -3.87975109     12.00592450     14.15406474
    C      5.55502496      3.50504402    -11.85174248      4.01688324     14.31370943    -25.54807887     -5.16902034

...

...
the energy：

 MD step:        1000
 Pressure:                                 -0.383377E-05 au    -0.112794E+09 Pa
 Potential Energy:                -489.0052946670 H       -13306.5111 eV
 MD Kinetic Energy:                  4.8434066848 H          131.7958 eV
 Total MD Energy:                 -484.1618879822 H       -13174.7153 eV
 MD Temperature:                     0.0112506543 au        3552.6714 K
4) MDRestartFrequency =10,  Steps = 10000
the trajectory:

288
MD iter: 1000
    C      5.98710489      5.94057875    -12.41871012      4.06664204    -34.63486869    -23.17202667      7.01749069
    C      5.76836868      5.15076367    -11.24571808      3.88134951    -13.36997681      1.53522439      8.53295750
    C      5.11529600      3.92355511    -12.01961265      4.02477468    -18.28411221    -21.51190262    -21.57539415

...

...
the energy：

MD step:        1000
 Pressure:                          -0.233664E-05 au    -0.687463E+08 Pa
 Potential Energy:                -489.1576845261 H       -13310.6578 eV
 MD Kinetic Energy:                  4.9975219502 H          135.9895 eV
 Total MD Energy:                 -484.1601625759 H       -13174.6683 eV
 MD Temperature:                     0.0116086456 au        3665.7160 K
...

...

The input is as follows,

Geometry = GenFormat {
  <<< "geom.gen"
}
Driver = VelocityVerlet {
  MovedAtoms = 1:-1
  Steps = 5000                # 5000 or 10000
  KeepStationary = Yes
  TimeStep [fs] = 1.0
  MDRestartFrequency = 1      #  10 or 1     
  OutputPrefix = "geom.out"
  Thermostat = None {}
  Velocities [AA/ps] = {               
   <<< "velocity.txt"
   }
   ConvergentForcesOnly = No
}
Hamiltonian = DFTB {
  SCC = Yes
  SCCTolerance = 1.0e-5
  MaxSCCIterations = 100
  EwaldParameter = 0.0
  OrbitalResolvedSCC = Yes
  Mixer = Broyden {
    MixingParameter = 0.2
    CachedIterations = -1
    InverseJacobiWeight = 1.000000000000000E-002
    MinimalWeight = 1.00000000000000
    MaximalWeight = 100000.000000000
    WeightFactor = 1.000000000000000E-002
  }
  MaxAngularMomentum = {
    C = "p"
  }
  Charge = 0.0
  SpinPolarisation = {}
  Filling = Fermi {
    Temperature [Kelvin] = 1000.0
  }
  SlaterKosterFiles = {
    C-C = "C-C.skf"
  }
  KPointsAndWeights = SupercellFolding{
  1   0   0
  0   1   0
  0   0   5
  0.0 0.0 0.0
  } 
  Dispersion = LennardJones{
   Parameters = UFFParameters{}
}                                     
  OldSKInterpolation = No
  OldRepulsiveSum = No
  ReadInitialCharges = No                      
}
Options = {
  WriteAutotestTag = No
  AtomResolvedEnergies = No
  WriteDetailedOut = Yes
  WriteEigenvectors = No
  WriteDetailedXML= No
  WriteBandOut = Yes
}
ParserOptions = {
  ParserVersion = 4
}



I would be really thankful for any help.
 Best regards

Xiaobao Zhang
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