RANDOM SEED: Difference between revisions

Revision as of 07:36, 8 April 2022

RANDOM_SEED = [integer][integer][integer]
Default: RANDOM_SEED = based on the system clock

Description: RANDOM_SEED specifies the seed of the random-number generator (compile VASP with -Dtbdyn).

The random-number generator (RNG) generates a sequence of random numbers for molecular-dynamics simulations for example to initialize atomic velocities and for the Andersen thermostat (MDALGO=1 | 11). The seed for the RNG determines the trajectory a molecular-dynamics simulation takes. Set the RANDOM_SEED tag to reproduce a previously performed calculation.

A typical input for the RANDOM_SEED looks like this:

RANDOM_SEED =         248489752                0                0

The initial value of RANDOM_SEED and the value after each MD step are written to the REPORT file.

Tip: The random seed is used to obtain reproducibility of exact numbers during every step. If the time-averaged results depend on the random seed, the ensemble is not big enough, i.e., the molecular-dynamics simulation time is too short.

@@ Line 12: / Line 12: @@
 The initial value of {{TAG|RANDOM_SEED}} and the value after each MD step are written to the {{FILE|REPORT}} file.
-{{NB|tip|The random seed should be set only if reproducibility of exact numbers during every step is required. If the result depends on the random seed, the ensemble is not big enough, i.e., the molecular-dynamics simulation time is too short.}}
+{{NB|tip|The random seed is used to obtain reproducibility of exact numbers during every step. If the time-averaged results depend on the random seed, the ensemble is not big enough, i.e., the molecular-dynamics simulation time is too short.}}
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