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## Re: Units

 From: Jean-Noël Grad Subject: Re: Units Date: Thu, 12 Dec 2019 13:19:05 +0100 User-agent: Mozilla/5.0 (X11; Linux i686; rv:68.0) Gecko/20100101 Thunderbird/68.2.2

```Hi,

```
The way I understand it, we define an arbitrary quantity of energy [E] to serve as a scale, to which we assign the value of the statistical thermal energy of the system, [E] = 300 kbT, which has the unit of Joules. We instantiate the electrokinetics class with a force density of 0.1 on the capacitor plates, so the value of the electric field E generated between the plates can be expressed as E = 0.1[E]/([q][x]) in simulation units (because V/m = J/C/m), which is equal to 0.1 * 4.14e-21 / 1.60e-19 / 1e-9 = 2.5875e6 J/C/m in SI units.
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The notation got me confused at first, because the electric field E has units of Volts/meter while the energy [E] has units of Joules.
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Best regards,
JN

On 12/11/19 6:46 PM, Ahmad Reza Motezakker wrote:
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```Dear EspressoMD users,

```
I am going through Tutorial 7: Electrokinetics​ and as you know it begins with SI unit conversion to Espresso units. There is a table which shows the necessary parameters for the simulation and their units. I have been able to convert all the parameters but the last one which is external electric fields (E).
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In other words, I am confused that how 2.585*10^6 (V/m) has been transferred to 0.1 [E]/[q][x].
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I really appreciate if you could help me with this. Thank you very much.

Best Regards,

```