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linuxeno

铁杆木虫 (正式写手)

[交流] 【求助】问nernst-einstern equation的计算处理

说实话,化学出身的,这些单位计算之类的真的这么多年已经忘的差不多了。。。

现在需要用这个方程计算一点东西,可是怎么都不知道单位上该怎么处理,只好请教物理方面的人来指点一下。。。。

现在一个模型需要处理载体电荷和其扩散运动产生的电导率之间的关系,
相互之间的关系已经被牛人们建立起来了。。。

谁能告诉我现在计算时,各变量的单位都是怎么处理的啊?以及用什么常数值啊?

式中的电荷单位该是什么呢?e还是1.6*10^-19C?
不知道该怎么处理,试算了几次结果都相差10个数量级以上。。。

实在是惭愧。。。各位指点一下吧。。。最好详细一点。。以前学的东西真的忘的没什么东西了
(指前因子A是没有单位的;电导率单位是S(西门子)/m;扩散系数标准单位是m^2/S(秒));浓度c的单位比如ppm应该是μg/g,所以影响不大吧;主要是这个charge carrier和boltzmann constant。。。自己怎么也凑不出来了(忘了电导率和这些之间的单位转换了)。。。

[ Last edited by linuxeno on 2009-9-19 at 23:23 ]
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bote

the unit of c is C/cm3, but not "ppm". it is

★ ★
linuxeno(金币+1):谢谢参与
ddx-k(金币+1,VIP+0):谢谢 9-22 19:42
the electron concentration but not the impurity content concentration in a material.

Boltzmann constant: J/K (SI)
charge: C (coulomb)   (SI)

Just sent you a note but not showed up here. Don't know why. inform me of your receiving or not. ths.
Find the absolute concentration of "H" in your sample. That is the quantity entering your expression of conductivity.

absolute concentration=[density of your sample/(mole mass*1.67*10^(-27))]*(relative concentration of H in ppm)
1.67*10^(-27) is the mass of a proton or neutron in the expression.

[ Last edited by bote on 2009-9-21 at 06:34 ]
2楼2009-09-20 13:21:32
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linuxeno

铁杆木虫 (正式写手)

thanks for your explanation.

In the original form of the Nernst-Einstein Equation, the unit of c seems that of electron.

However, in this revised equation, which relates the concentration and mobility (diffusion) of the charged species. In some papers, the electrical conductivity can be enhanced by the dissolution of H (proton) into solid materials, and in some papers which I am reading, the unit of c is ppm H and diffusion coefficient is also for H.

I am now trying to calculate the relation between H content, temperature and also electrical conductivity....

However, I always fail to get the right results...

In the paper, for example 100 ppm H, T=1573K, D=2.4E-10 m2/s, the charger carrier caused by H (q=+e) results in a conductivity of 0.01 S/m (A=unit 1).

Can you help me to use the above values for the evaluation?

[ Last edited by linuxeno on 2009-9-20 at 17:18 ]
3楼2009-09-20 17:05:01
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bote

read my first post again

read my first post again
4楼2009-09-21 06:47:03
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linuxeno

铁杆木虫 (正式写手)

thanks again
5楼2009-09-22 03:07:02
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