C***S
发帖数: 175 | 1 Any software or programme suggested?
I am trying to calculate some SAXS profile for polymer. I guess there should
be something ready for this work. I am totally green on this, any suggestions
are welcome.
Thanks! | o********e
发帖数: 34 | 2 For liquid (polymer in solutions) or crystal sample?
For polymer in solutions, the calculation for concentrated and dilute sample
are different.
Typcially, for concentrated samples, the so-called structure factor will
pollute your scattering profile. (Well, some people may like this
structure factor if they want to study the interactions.)
For dilute sample, things will be much easier. However, you still need
to have an idea of the conformation of your polymer before the calculation.
should
sug
【在 C***S 的大作中提到】
: Any software or programme suggested?
: I am trying to calculate some SAXS profile for polymer. I guess there should
: be something ready for this work. I am totally green on this, any suggestions
: are welcome.
: Thanks!
| C***S
发帖数: 175 | 3 solids. Well, I should say, less than 20% of crystal in amorphous
polymer matrix. any idea? Thanks!
Someone told me using some package from NIST. I am downloading it.
【在 o********e 的大作中提到】
: For liquid (polymer in solutions) or crystal sample?
: For polymer in solutions, the calculation for concentrated and dilute sample
: are different.
: Typcially, for concentrated samples, the so-called structure factor will
: pollute your scattering profile. (Well, some people may like this
: structure factor if they want to study the interactions.)
: For dilute sample, things will be much easier. However, you still need
: to have an idea of the conformation of your polymer before the calculation.
:
: should
| o********e
发帖数: 34 | 4 If it is amorphous polymer matrix, things will be very difficult.
Typically, unless you have a nice model, it is very difficult to obtain
a quantitative result.
I am not sure why you want to use SAXS to characterize your system.
I hope you still have some characteristic feature in your results which can be
linked
to the problem you want solve.
As far as I konw, unless you have already known the detail structure of
an amorphous system, it is almost impossible to quatitatively calculate
the scatte
【在 C***S 的大作中提到】
: solids. Well, I should say, less than 20% of crystal in amorphous
: polymer matrix. any idea? Thanks!
: Someone told me using some package from NIST. I am downloading it.
| C***S
发帖数: 175 | 5 I just need some simple qualitative comparison among different models.
I read some paper where they just need to know some geometry parameters,
and they can give the profile. But seems it is kind of too simple.
My model will be some clusters ditributed in polymer matrix. What I want
to do is, set up some gerometrical parameter of the clusters, and their
3D lattice, then, I can find some method to compute the SAXS profile.
I am learning the package from NIST. The problem is I have no control of
t
【在 o********e 的大作中提到】
: If it is amorphous polymer matrix, things will be very difficult.
: Typically, unless you have a nice model, it is very difficult to obtain
: a quantitative result.
: I am not sure why you want to use SAXS to characterize your system.
: I hope you still have some characteristic feature in your results which can be
: linked
: to the problem you want solve.
: As far as I konw, unless you have already known the detail structure of
: an amorphous system, it is almost impossible to quatitatively calculate
: the scatte
| b*******n
发帖数: 29 | 6 呵呵，我看到你的帖子很感兴趣，我的观点如下，
1，“3D lattice”， 远程的有序，如果你的样品不是各向同性，从2D的scattering
patten可以得到很多有关取向的信息（晶区的趋向）。
2， 如果你的样品是各向同性，你可以仿照 Fractal object dispersion 来套用
模型，可以得到clusters 的维数， primary particle size 等等信息。
3， 困难1： incoherent scattering 用背景减去不是很容易。困难2：structure
factor 很难近似为1。
can be
for
the
【在 C***S 的大作中提到】
: I just need some simple qualitative comparison among different models.
: I read some paper where they just need to know some geometry parameters,
: and they can give the profile. But seems it is kind of too simple.
: My model will be some clusters ditributed in polymer matrix. What I want
: to do is, set up some gerometrical parameter of the clusters, and their
: 3D lattice, then, I can find some method to compute the SAXS profile.
: I am learning the package from NIST. The problem is I have no control of
: t
| b*******n
发帖数: 29 | 7 amorphous solids?
知道密度和分子式不就可以算了吗？ | C***S
发帖数: 175 | 8 Polymer.
I am interesting in the shape of the clusters.
【在 b*******n 的大作中提到】
: amorphous solids?
: 知道密度和分子式不就可以算了吗？
| b*******n
发帖数: 29 | 9 I remembered that SiO2- amorphous polymer composites were well investigated
by SAXS or SANS in literature. What they need to calculate SLDs of polymers
are density and formula.
Most of classic models can deal with shapes including spheres (3D), plates
(2D)
and rods (1 D). 2.X D object is descriped as between shpere and plate. And
so on. SEM, TEM are always used to confirm the final shape.
the
【在 C***S 的大作中提到】
: Polymer.
: I am interesting in the shape of the clusters.
| o********e
发帖数: 34 | 10 You still need to know the structure of atoms to get accurate calculation.
For low angle scattering like SAXS or SANS, with SLD, you do not need detail
position of atoms. However, you still need to know the structure of
the different surface, for example, cylindle holes, etc., in order to
calculate the intensity with SLD.
For scattering technique, everything is about contrast.
Once you have a surface, there is scattering.
You need to know all the information of the surface which has contrast to
【在 b*******n 的大作中提到】
: amorphous solids?
: 知道密度和分子式不就可以算了吗？
| | | o********e
发帖数: 34 | 11 If you care about the shape of the bigger aggregated particles, scattering is
good at it. However, it also depends on the sample you use.
Again, for dilute conditions, the form factor of a particle can be very
accuratly caculated.
calculating
【在 b*******n 的大作中提到】
: I remembered that SiO2- amorphous polymer composites were well investigated
: by SAXS or SANS in literature. What they need to calculate SLDs of polymers
: are density and formula.
: Most of classic models can deal with shapes including spheres (3D), plates
: (2D)
: and rods (1 D). 2.X D object is descriped as between shpere and plate. And
: so on. SEM, TEM are always used to confirm the final shape.
:
: the
| o********e
发帖数: 34 | 12 Are these clusters embeded in a solid matrix?
If you can dissolve these cluster in some solvent with low volume
fraction(dilute condition), it will be much easier
to calculate the form factor.
the
【在 C***S 的大作中提到】
: Polymer.
: I am interesting in the shape of the clusters.
| o********e
发帖数: 34 | 13 I agree.
Nod nod. That is why it is so difficult to get accurate shape information of
clusters in solid. Structure factor is always the killing factor.
I think the incoherent scattering is not a big issue. He can always treat it
as a fitting parameter since incoherent scattering is always the same at
different scattering wavevector.
Are you a scattering guy? | b*******n
发帖数: 29 | 14 The arrangement of atoms is a very tough work for SANS or SAXS.
I guess the reliable q range of CPMAS data is from 0.004 ~ 1 (A-1).
olivertree , could you tell me the typical q range of low angle scattering?
if we regard amorphous solid as liquid, I can list a lot of perfect model
fitting.
dilute
need
【在 o********e 的大作中提到】
: You still need to know the structure of atoms to get accurate calculation.
: For low angle scattering like SAXS or SANS, with SLD, you do not need detail
: position of atoms. However, you still need to know the structure of
: the different surface, for example, cylindle holes, etc., in order to
: calculate the intensity with SLD.
: For scattering technique, everything is about contrast.
: Once you have a surface, there is scattering.
: You need to know all the information of the surface which has contrast to
| b*******n
发帖数: 29 | 15 In fact, incoherent scattering can result in a poor transmission at high
q, which makes the data terrible looking without proper background
subtraction.
By the way, I am a polymer guy.
【在 o********e 的大作中提到】
: I agree.
: Nod nod. That is why it is so difficult to get accurate shape information of
: clusters in solid. Structure factor is always the killing factor.
: I think the incoherent scattering is not a big issue. He can always treat it
: as a fitting parameter since incoherent scattering is always the same at
: different scattering wavevector.
: Are you a scattering guy?
| C***S
发帖数: 175 | 16 Yes.
I am working on NMR and we find the model of Nafion is somewhat
not in detail enough. And we think the clusters in Nafion is somewhat
not in spherical. So, we want to find a computation method to calculate
the SAXS profile and compare with the experimental SAXS data.
Now what I am looking for is to generate some geometry model, say cylinders
ditributed in space, and computate the profile.
I do not want to generate the atomic level accuracy.
【在 o********e 的大作中提到】
: Are these clusters embeded in a solid matrix?
: If you can dissolve these cluster in some solvent with low volume
: fraction(dilute condition), it will be much easier
: to calculate the form factor.
:
: the
| o********e
发帖数: 34 | 17 I only know some of them.
However, most of parameters of SANS and SAXS instruments can be found in
their webpages.
For SANS, the typical range: 0.004~A-1 to 0.6~A-1.
With reactor source based SANS, it can reach 0.001~A-1.
The high Q range can also be improved with smaller wave length.
For SAXS, I am not exact sure. However, it should be able to reach
0.004~A-1, with larger high Q range. However, it is said that
it is very difficult to get samller Q range.
I am not sure what you mean by "regard a
【在 b*******n 的大作中提到】
: The arrangement of atoms is a very tough work for SANS or SAXS.
: I guess the reliable q range of CPMAS data is from 0.004 ~ 1 (A-1).
: olivertree , could you tell me the typical q range of low angle scattering?
: if we regard amorphous solid as liquid, I can list a lot of perfect model
: fitting.
:
: dilute
: need
| C***S
发帖数: 175 | 18 Yes. The q range is what you said.
【在 b*******n 的大作中提到】
: The arrangement of atoms is a very tough work for SANS or SAXS.
: I guess the reliable q range of CPMAS data is from 0.004 ~ 1 (A-1).
: olivertree , could you tell me the typical q range of low angle scattering?
: if we regard amorphous solid as liquid, I can list a lot of perfect model
: fitting.
:
: dilute
: need
| o********e
发帖数: 34 | 19 I happen to read some papers talking about Nafion with scattering technique.
Not sure about the detial now.
My feeling is that the structure of Nafion depends on the hydration level.
Some people propose a series of different structures at different hydration
levels. However, those model is not well justified. Also the feature
of the scattering is not very rich enough to give more information.
This is going to be a tough job for you if you want to know the shape
of holes or clusters in Nafion. Do
【在 C***S 的大作中提到】
: Yes.
: I am working on NMR and we find the model of Nafion is somewhat
: not in detail enough. And we think the clusters in Nafion is somewhat
: not in spherical. So, we want to find a computation method to calculate
: the SAXS profile and compare with the experimental SAXS data.
: Now what I am looking for is to generate some geometry model, say cylinders
: ditributed in space, and computate the profile.
: I do not want to generate the atomic level accuracy.
| C***S
发帖数: 175 | 20 Last question first.
Once you keep Nafion in ambient condition, it is soft.But in dry state,
it is kind of rigid film. this can happen in a minute. When you handle this
film, the sweat from your hand can also change the film.
From NMR, we have some idea of what the clusters look like, so we want to see
if we are right, what the SAXS profile would be.
【在 o********e 的大作中提到】
: I happen to read some papers talking about Nafion with scattering technique.
: Not sure about the detial now.
: My feeling is that the structure of Nafion depends on the hydration level.
: Some people propose a series of different structures at different hydration
: levels. However, those model is not well justified. Also the feature
: of the scattering is not very rich enough to give more information.
: This is going to be a tough job for you if you want to know the shape
: of holes or clusters in Nafion. Do
|
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