[DFTB-Plus-User] MD output looks the same as all the steps with NPT ensemble

[Ben Hourahine]

Hello Muhammad,

the problem is the time step:

  TimeStep = 1.0e-15                #Time interval between two MD steps


If no units are supplied, DFTB+ defaults to atomic units (not SI). See
the manual for details how to set this, but something like

TimeStep [Femtosecond] = 1.0


is probably what you wanted.

Regards

Ben

On 17/12/15 21:50, Faruq, Muhammad wrote:
> Dear All 
> Could you please help me to find out the problem from my MD calculations. It looks to me the first step  and the last step all are the same volume as well as energy. In this calculation,  I used NPT ensemble so that volume should be changed at each  step.  Here is the output and input details. Any help will be appreciated and thanks in advance 
>
> Kind Regards
> Muhammad Faruq
> University of Bolton
>  
> MD step:           0
> Volume:                             0.130165E+05 au^3
>  Pressure:                           0.166809E-02 au     0.490769E+11 Pa
>  Potential Energy:                -326.3118416085 H        -8879.3970 eV
>  MD Kinetic Energy:                  0.0000024000 H            0.0001 eV
>  Total MD Energy:                 -326.3118392085 H        -8879.3969 eV
>  MD Temperature:                     0.0000000100 au           0.0032 K
>
> MD step:        1410
>  Nose-Hoover chain variables
>  x:
>     0.1000000000E+01    0.1000000000E+01    0.1000000000E+01
>  v:
>    -0.7044897072E-08   -0.7046621982E-08   -0.7046621982E-08
>  g:
>    -0.9999981342E+04   -0.1000000000E+05   -0.1000000000E+05
> Lattice vectors (A)
>   1.244800000000E+01  0.000000000000E+00  0.000000000000E+00
>   0.000000000000E+00  1.244800000000E+01  0.000000000000E+00
>   0.000000000000E+00  0.000000000000E+00  1.244800000000E+01
>  Volume:                             0.130165E+05 au^3
>  Pressure:                           0.166810E-02 au     0.490772E+11 Pa
>  Potential Energy:                -326.3118436796 H        -8879.3970 eV
>  MD Kinetic Energy:                  0.0000024000 H            0.0001 eV
>  Total MD Energy:                 -326.3118412796 H        -8879.3970 eV
>  MD Temperature:                     0.0000000100 au           0.0032 K
>
> MD step:        5080
>  Nose-Hoover chain variables
>  x:
>     0.1000000000E+01    0.1000000000E+01    0.1000000000E+01
>  v:
>    -0.2539484575E-07   -0.2539662198E-07   -0.2539662198E-07
>  g:
>    -0.9999894883E+04   -0.1000000000E+05   -0.1000000000E+05
> Lattice vectors (A)
>   1.244800000000E+01  0.000000000000E+00  0.000000000000E+00
>   0.000000000000E+00  1.244800000000E+01  0.000000000000E+00
>   0.000000000000E+00  0.000000000000E+00  1.244800000000E+01
>  Volume:                             0.130165E+05 au^3
>  Pressure:                           0.166810E-02 au     0.490772E+11 Pa
>  Potential Energy:                -326.3118436796 H        -8879.3970 eV
>  MD Kinetic Energy:                  0.0000024000 H            0.0001 eV
>  Total MD Energy:                 -326.3118412796 H        -8879.3970 eV
>  MD Temperature:                     0.0000000100 au           0.0032 K
>
> Here is Input file: 
>
> Geometry = GenFormat {
> <<< Cu5Si.gen
> }
>
> Driver = VelocityVerlet {
>   MovedAtoms =  "1:-1"
>  # Steps = 250
>   TimeStep = 1.0e-15                #Time interval between two MD steps
>   KeepStationary = No               #Remove translational motion from the system
>   MDRestartFrequency=10
>   Velocities = {}
>   ConvergentForcesOnly = No
>
>   Barostat = {
>     Pressure = 0
>     Timescale =10
>   }
>
>   Thermostat = NoseHoover{
>     Temperature [Kelvin] = TemperatureProfile { # Temperatures in K
>       constant 1    0.0 # Setting T=10 K for the 0th MD-step
>       linear   250 300.0 # Linearly rising T in  250 steps up to T=300 K
>       linear   1415 2000.0 # Linearly rising T in  1415 steps up to T=2000 K by rate 1.2K/fs
>       constant 2000 2000.0 # Constant T through 2000 steps
>       exponential 1415 300.0 # Exponential decreasing in 1415 steps to T=300K
>     }
>     CouplingStrength=100
>    IntegratorSteps = 1
>   }
>   OutputPrefix = "final_geo"
> }
>
> Hamiltonian = DFTB {
>   SCC = Yes
> SCCTolerance = 1.0e-5
>   EwaldParameter = 0.1
>   MaxSCCIterations = 10
>   Mixer = Broyden {
>     MixingParameter = 0.2
> }
>
>   MaxAngularMomentum = {
>     Cu = "d"
>     Si = "d"
>   }
>
>   Filling = Fermi {} 
>   SlaterKosterFiles = Type2FileNames {
>     Prefix = "/home/maf2mpo/FAST_cal_Others/DFTB+/sk/matsci-0-3/"
>     Separator = "-"
>     Suffix = ".skf"
>   }
>
>   KPointsAndWeights = {
>     0.0  0.0  0.0  1.0
>   }
> ReadInitialCharges = Yes
> }
> Options = {
>   WriteEigenvectors = No
>   WriteResultsTag = Yes
>   WriteDetailedOut = Yes
>   WriteBandOut = Yes
>   }
>
>
>
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-- 
      Dr. B. Hourahine, SUPA, Department of Physics,
    University of Strathclyde, John Anderson Building,
            107 Rottenrow, Glasgow G4 0NG, UK.
    +44 141 548 2325, benjamin.hourahine at strath.ac.uk

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