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23 Oct 2021 03:04:03 EDT (-0400)
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From: Samuel B 
Subject: Re: Granite_21 - the final macro
Date: 15 Sep 2021 19:25:00
Message: <web.6142808fb21f010ccb705ca46e741498@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> (...)
> Only, as a freshman, I was not particularly interested in
> this branch of geology! Hammering away at overturned, anticlinal rock
> sections: /That/ was what life was about! ;-)

Yeah, being out in the field is wonderful. I know our reasons for being out
there were for different reasons, but I also know the thrill of finding
something interesting and tracking it down. I really miss it.

> Op 14/09/2021 om 01:14 schreef Samuel B.:
> > It is a cool program, I just wish I could figure out my HKL issues so I can do
> > more with it. (My previous searches didn't turn up much useful info, or maybe I
> > wasn't comprehending what I saw...)
> >
> I know what you mean. These are a couple sites which explain the use of
> the Wulff net. There are more of course, but these are fairly basic.
>
> http://www.minsocam.org/ammin/AM25/AM25_689.pdf
> https://www.doitpoms.ac.uk/tlplib/stereographic/wulff_construct.php
>
> However, to tell the truth, I remain a bit baffled when I see those
> things again, after all those years. I am not really sure I understand;
> I think you are more familiar with all this.

No, I don't think I'm any more familiar with these things than you are...
probably less so. Thanks for the links. But I looked at them and to be honest,
the information looks very thick. So thick I'm not actually sure if it would be
any help in my endeavors...


Sam


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From: Thomas de Groot
Subject: Re: Granite_21 - the final macro
Date: 16 Sep 2021 02:45:55
Message: <6142e823$1@news.povray.org>
Op 16/09/2021 om 01:23 schreef Samuel B.:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> (...)
>> Only, as a freshman, I was not particularly interested in
>> this branch of geology! Hammering away at overturned, anticlinal rock
>> sections: /That/ was what life was about! ;-)
> 
> Yeah, being out in the field is wonderful. I know our reasons for being out
> there were for different reasons, but I also know the thrill of finding
> something interesting and tracking it down. I really miss it.
> 
I can understand that.

>> Op 14/09/2021 om 01:14 schreef Samuel B.:
>>> It is a cool program, I just wish I could figure out my HKL issues so I can do
>>> more with it. (My previous searches didn't turn up much useful info, or maybe I
>>> wasn't comprehending what I saw...)
>>>
>> I know what you mean. These are a couple sites which explain the use of
>> the Wulff net. There are more of course, but these are fairly basic.
>>
>> http://www.minsocam.org/ammin/AM25/AM25_689.pdf
>> https://www.doitpoms.ac.uk/tlplib/stereographic/wulff_construct.php
>>
>> However, to tell the truth, I remain a bit baffled when I see those
>> things again, after all those years. I am not really sure I understand;
>> I think you are more familiar with all this.
> 
> No, I don't think I'm any more familiar with these things than you are...
> probably less so. Thanks for the links. But I looked at them and to be honest,
> the information looks very thick. So thick I'm not actually sure if it would be
> any help in my endeavors...
> 
Yeah... I know what you mean. One of the reasons I didn't get very far 
in crystallography. I have some 3D visualisation skills :-) but these 
kind of exercises always left me profoundly baffled I confess. Otoh, I 
believe they /may/ unlock certain geometrical symmetry problems proper 
to certain mineral classes.

-- 
Thomas


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From: Bald Eagle
Subject: Re: Granite_21 - the final macro
Date: 16 Sep 2021 06:30:00
Message: <web.61431c5fb21f010c1f9dae3025979125@news.povray.org>
"Samuel B." <stb### [at] hotmailcom> wrote:

> > Nice little program indeed! Thanks. Wulff-nets, ha! That was not really
> > my cup of tea... ;-)
>
> I don't even know a Wulff net is. But based on its appearance, I'm guessing it's
> some sort of mapping between HKL indices and a sphere. Maybe it's a clue to help
> me convert HKL values to planes...
>

> It is a cool program, I just wish I could figure out my HKL issues so I can do
> more with it. (My previous searches didn't turn up much useful info, or maybe I
> wasn't comprehending what I saw...)


Aren't the HKL values just the vector normals of the planes?
That's what the wikipedia articles suggested on my brief skim.

Would not plane {y, 0} have an hkl index of <0,1,0>?

Not sure what the overall goal is, so not sure what to suggest to test this.

- Bill


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From: Thomas de Groot
Subject: Re: Granite_21 - the final macro
Date: 16 Sep 2021 07:48:48
Message: <61432f20$1@news.povray.org>
Op 16-9-2021 om 12:28 schreef Bald Eagle:
> "Samuel B." <stb### [at] hotmailcom> wrote:
> 
>>> Nice little program indeed! Thanks. Wulff-nets, ha! That was not really
>>> my cup of tea... ;-)
>>
>> I don't even know a Wulff net is. But based on its appearance, I'm guessing it's
>> some sort of mapping between HKL indices and a sphere. Maybe it's a clue to help
>> me convert HKL values to planes...
>>
> 
>> It is a cool program, I just wish I could figure out my HKL issues so I can do
>> more with it. (My previous searches didn't turn up much useful info, or maybe I
>> wasn't comprehending what I saw...)
> 
> 
> Aren't the HKL values just the vector normals of the planes?
> That's what the wikipedia articles suggested on my brief skim.
> 
> Would not plane {y, 0} have an hkl index of <0,1,0>?
> 
> Not sure what the overall goal is, so not sure what to suggest to test this.
> 
If I remember correctly, that is indeed the case I believe.

-- 
Thomas


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From: Bald Eagle
Subject: Re: Granite_21 - the final macro
Date: 16 Sep 2021 13:30:00
Message: <web.61437e38b21f010c1f9dae3025979125@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:

> > Aren't the HKL values just the vector normals of the planes?
> > That's what the wikipedia articles suggested on my brief skim.
> >
> > Would not plane {y, 0} have an hkl index of <0,1,0>?
> >
> > Not sure what the overall goal is, so not sure what to suggest to test this.
> >
> If I remember correctly, that is indeed the case I believe.
>
> --
> Thomas

So then, to some degree, the unit cell for the crystal should be some form of
intersection between all of the planes that the hkl indices define. (?)  Does
the file format include any data that would serve as an offset?

Creating the most basic crystal shapes, probably starting with cubic NaCl, might
give a clue as to how to code an implementation of that notational system.


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From: Samuel B 
Subject: Re: Granite_21 - the final macro
Date: 16 Sep 2021 19:00:00
Message: <web.6143cc4fb21f010ccb705ca46e741498@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Samuel B." <stb### [at] hotmailcom> wrote:
> Aren't the HKL values just the vector normals of the planes?
> That's what the wikipedia articles suggested on my brief skim.
>
> Would not plane {y, 0} have an hkl index of <0,1,0>?

That's probably the case with simple cubic crystal systems. Other systems, like
hexagonal, monoclinic, etc., are a bit different. I should try to get a cubic
system to work first.

> Not sure what the overall goal is, so not sure what to suggest to test this.

My goal is to simply convert HKL values to normal vectors, and then to build
crystals from those using intersecting planes.

Sam


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From: Samuel B 
Subject: Re: Granite_21 - the final macro
Date: 16 Sep 2021 19:15:00
Message: <web.6143cf38b21f010ccb705ca46e741498@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>
> > > Aren't the HKL values just the vector normals of the planes?
> > > That's what the wikipedia articles suggested on my brief skim.
> > >
> > > Would not plane {y, 0} have an hkl index of <0,1,0>?
> > >
> > > Not sure what the overall goal is, so not sure what to suggest to test this.
> > >
> > If I remember correctly, that is indeed the case I believe.
> >
> > --
> > Thomas
>
> So then, to some degree, the unit cell for the crystal should be some form of
> intersection between all of the planes that the hkl indices define. (?)

I think the unit cell defines the dimensions and angles. Attached is a
screenshot from KrystalShaper. The thin-lined, skewed box surrounding the
crystal represents the unit cell. In the lower right area of the image you can
see the numbers "4.913 x 4.913 x 5.4045" which are probably the dimensions of
the cell. The numbers "90 90 120" are the angles. But how to convert these to
proper planes? All my attempts have failed. There is probably a basic solution
and I'm just over-complicating things...

> Does the file format include any data that would serve as an offset?

The data files are in some non-human-readable format. I should probably get a
hex editor and take a look.

> Creating the most basic crystal shapes, probably starting with cubic NaCl, might
> give a clue as to how to code an implementation of that notational system.

Yes, I should start with the most basic thing first.

Sam


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Attachments:
Download 'krystalshaper-quartz.png' (18 KB)

Preview of image 'krystalshaper-quartz.png'
krystalshaper-quartz.png


 

From: Bald Eagle
Subject: Re: Granite_21 - the final macro
Date: 17 Sep 2021 06:30:00
Message: <web.61446d55b21f010c1f9dae3025979125@news.povray.org>
"Samuel B." <stb### [at] hotmailcom> wrote:
In the lower right area of the image you can
> see the numbers "4.913 x 4.913 x 5.4045" which are probably the dimensions of
> the cell. The numbers "90 90 120" are the angles. But how to convert these to
> proper planes? All my attempts have failed. There is probably a basic solution
> and I'm just over-complicating things...

I agree that those are the dimensions and angles.
But they are the angles of the unit cell, and ATM I fail to see how you need
them.

What I DO see, is that you have numerical triplets, indicating the hkl indices.
I believe that you can simply use those numbers as the normal vectors for all of
the face planes.  Maybe there's a way to display them with greater precision.
Still not sure about the offset, but maybe once you get the ball rolling, some
light will be shed on that aspect of the data.

Perhaps if there are tables of human readable hkl indices for different crystal
structures, you can compare and contrast and discern a pattern.

And that's all I have before 1st coffee.   :D


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From: Samuel B 
Subject: Re: Granite_21 - the final macro
Date: 18 Sep 2021 17:05:00
Message: <web.6146538cb21f010ccb705ca46e741498@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Samuel B." <stb### [at] hotmailcom> wrote:
> In the lower right area of the image you can
> > see the numbers "4.913 x 4.913 x 5.4045" which are probably the dimensions of
> > the cell. The numbers "90 90 120" are the angles. But how to convert these to
> > proper planes? All my attempts have failed. There is probably a basic solution
> > and I'm just over-complicating things...
>
> I agree that those are the dimensions and angles.
> But they are the angles of the unit cell, and ATM I fail to see how you need
> them.

I think they merely point to the angles and dimensions one would need when
converting HKL indices into proper plane normals. For a cubic system, this would
be straightforward, but for a hexagonal system, something else is needed. I
tried shearing/skewing & scaling cubic coords to produce proper results, but as
said before, I had no luck.

> What I DO see, is that you have numerical triplets, indicating the hkl indices.
> I believe that you can simply use those numbers as the normal vectors for all of
> the face planes.  Maybe there's a way to display them with greater precision.

There is no greater precision. Attached is an image showing the table of HKL
indices of a basic quartz crystal. When you click on any number field, you'll
find it's just an integer. (Except for the distance values, of course.) If I'm
not mistaken, this is because the HKL system only works for the intended
coordinate spaces (aka unit cells).

> Still not sure about the offset, but maybe once you get the ball rolling, some
> light will be shed on that aspect of the data.

Not sure what you mean. The plane offsets? Those are given by the aforementioned
fourth value, "distance."

> And that's all I have before 1st coffee.   :D

Drink 'em if you've got 'em! ;)

Sam


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Attachments:
Download 'krystalshaper-quartz-indices.png' (7 KB)

Preview of image 'krystalshaper-quartz-indices.png'
krystalshaper-quartz-indices.png


 

From: Thomas de Groot
Subject: Re: Granite_21 - the final macro
Date: 20 Sep 2021 03:02:01
Message: <614831e9$1@news.povray.org>
Not sure if this might help: http://jcrystal.com/products/winwulff/

I am still thinking how this would help. Fifty five years ago (!) when I 
was introduced to the use of a Wulff net, you were given the model of a 
crystal with the task to translate its features onto the net, 
determining the symmetry planes, the axes of rotation, measuring the 
angles between faces, etc. I suppose the difficulty here is to do the 
opposite, or am I wrong?

-- 
Thomas


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