Dynamics Database

Introduction

A Dynamics database is created when the dynamics BTCL command is invoked. The Dynamics database is of type Dynamics in the CurrentDatabase table.

Two (2) tables are always created along with the database:

The Properties table contains two (2) columns, Name (type = string) and Value (type = double) which give the name and the value of some of the properties in a dynamics run. Some of the properties reported are number of degrees of freedom, kinetic energy, total energy, temperature, and, for periodic systems, volume, density, pressure, stress, strain, and cell parameters.

The Coord table contains two (2) columns, Velocity (type = double) and Acceleration (type = double), which give the velocities and accelerations of the asymmetric, movable atoms in the system.

Example - Accessing the Dynamics Database during a Dynamics Run

First create a database handle. This can be done any time that dynamics is running, but may be best to do so before the dynamics run starts, for reasons of efficiency.

BTCL > dynamics time = 10 \
        execute +before frequency = 0 \
          command = {database handle dyn_h Dynamics.; database print $dyn_h} \
        execute frequency = 1 before = 1 after = 1 \
          command = {$dyn_h print Properties; $dyn_h print Coord}

In this example, we get the dynamics database handle before dynamics starts and print it out. We also print out the Properties table before, during (every step), and after dynamics.

Sample output of the Properties and Coord tables are:

The Properties table:

{
    Row  Name            Value    
    ---  --------------  -------  
     0)  DegreesFreedom    24.00
     1)  KineticEnergy      7.10
     2)  TotalEnergy     -132.78
     3)  Temperature      298.00
     4)  Volume           112.99
     5)  Density            2.65
     6)  Pressure          10.19
     7)  StressXX         -12.78
     8)  StressYY          -9.75
     9)  StressZZ          -8.03
    10)  StressXY           1.54
    11)  StressXZ          -0.23
    12)  StressYZ          -0.40
    13)  StrainXX           0.00
    14)  StrainYY           0.00
    15)  StrainZZ           0.00
    16)  StrainXY           0.00
    17)  StrainXZ           0.00
    18)  StrainYZ           0.00
    19)  A                  4.91
    20)  B                  4.91
    21)  C                  5.41
    22)  Alpha             90.00
    23)  Beta              90.00
    24)  Gamma            120.00
    25)  Boltzmann          1.00
}

The Coord table:

{
    Row  Velocity                              Acceleration

    ---  ------------------------------------  ---------------------------------

     0)  {  0.0000000  0.0000000  0.0000000 }  {  0.000000  0.000000  0.000000 }
     1)  {  0.0000000  0.0000000  0.0000000 }  {  0.000005  0.000000 -0.000001 }
     2)  {  0.0000000 -0.0006231  0.0000000 }  {  0.000000 -0.003234  0.000000 }
     3)  {  0.0004435  0.0002521  0.0002062 }  { -0.000333  0.000034 -0.001037 }
     4)  { -0.0000482  0.0000000  0.0006467 }  {  0.000124  0.000000  0.000188 }
     5)  { -0.0009549 -0.0000133 -0.0000301 }  {  0.000033  0.000057  0.000335 }
     6)  { -0.0002096  0.0004364 -0.0005672 }  {  0.003730  0.000752  0.012754 }
     7)  { -0.0001985  0.0000000 -0.0000706 }  {  0.000428  0.000000  0.000079 }
}

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