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redskywei

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[交流] 【求助】castep中光學(xué)性能吸收反射譜的單位是什么？

請問，castep中計(jì)算光學(xué)性能的吸收譜中，單位是什么？
他的幫助里沒找到相關(guān)的說明，另外，這個(gè)吸收系數(shù)為什么這么高？我算的碳管吸收有的峰值30000這么多。請高人給俺解惑一下。
反射系數(shù)的話就是簡單的強(qiáng)度反射率了吧，可以認(rèn)為是沒有單位么？這個(gè)參量中峰值最大的才0.04. 不知道這么理解對否。

這里現(xiàn)行謝過。

我在幫助里仔細(xì)又找了一下，找到了相關(guān)公式，可是里面的量的說明還是不能讓我得出吸收系數(shù)的單位是啥。我在5.0的Optical properties->Definition of optical constants下看到了公式，內(nèi)容如下（公式不知道怎么能搞上了，呵呵）：CASTEP can calculate the optical properties of solids that are due to electronic transitions.

In general, the difference in the propagation of an electromagnetic wave through vacuum and some other material can be described by a complex refractive index, N:

Eq. CASTEP 48

In vacuum N is real, and equal to unity. For transparent materials it is purely real, the imaginary part being related to the absorption coefficient by:

Eq. CASTEP 49

The absorption coefficient indicates the fraction of energy lost by the wave when it passes through the material, so that the intensity at the distance x from the surface is I(x)=I(0)exp(-2πηx), where I(0) is the intensity of the incident light.

The reflection coefficient can be obtained for the simple case of normal incidence onto a plane surface by matching both the electric and magnetic fields at the surface:

Eq. CASTEP 50

However, when performing calculations of optical properties it is common to evaluate the complex dielectric constant and then express other properties in terms of it. The complex dielectric constant, ε(ω), is given by:

Eq. CASTEP 51

and hence the relation between the real and imaginary parts of the refractive index and dielectric constant is:

Eq. CASTEP 52

Another frequently used quantity for expressing optical properties is the optical conductivity, σ(ω):

Eq. CASTEP 53

Optical conductivity is usually used to characterize metals, however CASTEP is aimed more toward the optical properties of insulators and semiconductors. The main difference between the two is that intraband transitions play important role in the IR part of the optical spectra of metals and these transitions are not considered at all in CASTEP.

A further property that can be calculated from the complex dielectric constant is the energy loss function. It describes the energy lost by an electron passing through a homogeneous dielectric material and is given by:

Eq. CASTEP 54

還請高人不吝賜教～～～

[ Last edited by redskywei on 2010-11-29 at 20:28 ]

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1樓 2010-11-29 12:25:19

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木蟲 (正式寫手)

redskywei(金幣+1):我找到公式了，就是無法算出來是cm-1還是m-1，否則相差100倍哦 2010-11-29 21:23:50

反射率和吸收譜的公式在黃昆的固體物理上有。

贊一下

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5樓2010-11-29 20:21:51

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bashen1

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★ ★
redskywei(金幣+2):謝謝參與
redskywei(金幣+1):物理單位呢，該如何表示？ 2010-11-29 12:52:22
zzy870720z(金幣+1):謝謝交流 2010-11-29 22:45:29

應(yīng)該是透射率的倒數(shù)，取自然對數(shù)后就是吸收系數(shù)了

贊一下(3人)

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2樓2010-11-29 12:31:55

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lzl8181

鐵桿木蟲 (著名寫手)

★
redskywei(金幣+2):謝謝參與

據(jù)我推算吸收系數(shù)的單位為1/cm，但一直沒找到太有力的證據(jù)，如果哪位有金剛石吸收系數(shù)的實(shí)驗(yàn)值就好了。
從Help中的幫助文件可以看出，CASTEP中的反射系數(shù)就是反射率：？%。

贊一下(1人)

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3樓2010-11-29 12:57:36

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redskywei(金幣+2):謝謝參與
redskywei(金幣+1):就是沒找到導(dǎo)出公式，能給打出來么？ 2010-11-29 19:51:34

吸收譜應(yīng)該是cm-1,反射譜是反射系數(shù)，沒有量綱�？催@兩個(gè)的導(dǎo)出公式就知道了。不放心可以用介電譜自己算。

贊一下(1人)

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4樓2010-11-29 13:22:14

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