Description
Return spherical translational Stokes-Einstein diffusivity.
Diffusive and thermal scales depend on dimensionality, geometry, drag and compatible energy/time units. A local displacement correction or ideal spherical diffusivity is distinct from fitting a stochastic trajectory or establishing that a measured system satisfies the model.
Return spherical translational Stokes-Einstein diffusivity.
When to use this tool
Use Diffusion Stokes Einstein Radius Factor when checking the stated diffusion, drift, work or thermal-energy convention.
How to use the tool and how it works
- Enter thermalEnergy, viscosity, radius. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read diffusivity. Use the output convention below.
Return spherical translational Stokes-Einstein diffusivity. Require thermalEnergy >= 0 and viscosity/radius > 0; diffusivity = thermalEnergy/(6*pi*viscosity*radius).1
Stokes drag describes a sphere in an appropriate viscous-flow regime. The low-Reynolds assumption must be checked separately before using a derived transport scale.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| thermalEnergy | Thermal Energy | Required. Finite number; minimum 0. |
| viscosity | Viscosity | Required. Finite number; strictly above 0. |
| radius | Radius | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| diffusivity | Diffusivity | Required. Finite number. |
{
"input": {
"thermalEnergy": 18.84955592153876,
"viscosity": 2,
"radius": 3
},
"output": {
"diffusivity": 0.16666666666666666
}
}Limitations and assumptions
- This assumes continuum, no-slip spherical drag and compatible units; confinement, shape and non-Newtonian effects are not included.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use calibrated trajectories and an appropriate geometry/noise/transport model for fitted diffusion parameters, uncertainty or molecular mechanisms.
References
Similar or alternative tools
- Rotational Diffusion Viscosity Radius Term
Return spherical rotational diffusivity and second-rank correlation time.
- Diffusion Time Scale Ratio
Return a ratio of diffusive time scales.