Many moons ago, the teacher, who spent 5 or 6 year in Moscow on XRD of quartz, could explain all things crystally clear, and we were wondering what he was doing spending so many years on XRD of the simplest mineral in front the primitive instrument.
one of the good thing we learned was that after you plot the planes (which are many dots) in the reciprocal space, then you would start drawing spheres with radius of 2sin(theta)/lamda. so when the sphere intercepts the dots, that's where r=1/d. then at this 2theta angle, interference is strong. Using the same principle, you can find the intensity of the peak.
This plot certainly does not look elegant as the Debye formula. But it is so easy to remember: the radius is proportional to 2theta at small angle or 2sin(theta). Certainly if the mineral is center symmetric, you can add another dot in the 3rd quadrant; so on so forth. it changes the multiplicity but the graph remains valid.
The refFmult function is useful when there are two subphases of the same mineral; for example, you can have some detrital kaolinite and some authigenic kaolinite crystals in the same rock; the representation of the detrital one will be a large dot, whereas of the authigenic one will be a smaller one. both at the same position in the reciprocal space. certainly you can write two str files; linking the basic cell parameters. Or to make life easier, you can use reFmult function in the str file.
Found a graph from Dr. Kleeberg. here it is
once this reFmult is defined, most of the descriptors can be parameterized into arrays.
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Before I wrote anything XRD, I wrote stories using various alias. I just finishing translating this one
Huashan Mountain； an excursion
[the story was first published in Chinese: mixing the present tense with the past makes me feel right]
Huashan is a beautiful mountain that attracts hundreds of thousands of visitors annually. Many years ago when I went to college, there were segments of wood planks on 70 to 80 degree rock surfaces; almost vertical. Some segments have only carved foot holds and some others only wood planks; there was a iron chain to grab on, but no harness and no railing. Also, there was no alternative to bypass these dangerous segments to the top of the mountain.
The following picture from the internet shows the same path, but with both foothold AND a plank of wood. More importantly, a steel rope is put there and visitors nowadays are wearing harnesses. The safety factor is at least ten times higher than it was.
On one end of the narrow plank path, there are very steep and very narrow steps carved out of the granitic rock, Climbing up is much easier than getting down.
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A few days back, an old friend, W, visited us in Houston with his family. He was an old classmate of mine. When we parted after graduation, each of us was single; now both of us are married with kids. The wives got acquainted very fast, and topics were on kids and shopping deals. Then there was a proud display of the deals my wife got.
W looked quite macho, obviously muscular in the upper body; his wife was petite; On the dinner table, my wife said, "look at W, he keeps such a good figure, you need follow him to the gym more often, instead of eating like hog each meal".
The smile on W's face disappeared, and I knew something reminded him of C. whether was Camille or Camylla, I didn't remember and never had the courage to ask.
How they got together escaped me but I can never forget their ending. When W and his wife were leaving, I asked whether I could write down this story; he agreed, but would like to keep his identity unrevealed.
_________________________his story___________________________
We met the first day of school on the registration day.
It was hot. Ninety degrees. Students got the paperwork done and started dragging the luggage towards the dorm. I was turning around the building and found C sitting on the curb. One wheel on her luggage was broken.
Mine had big wheels. A Hi from me and She smiled back. I offered to carry her luggage on top of mine as she's heading to the same direction.
We started to chat. we came from the neighboring towns. If my GPA had been 0.2 point higher, we could've ended in the same high school.
Certainly, it was never too late. We were here on the college campus, chatting while walking. For a moment, I wished that she wasn't so chubby. But her character was definitely an attracting one.
The feeling that day was mutual. Both understood for the first time what was love at first sight.
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Busy classes. Projects; Field trips; the mundane college stuff for other kids.
These years were my best years; and hers, too. Happy days outnumbered strained ones by 100 to 1.
A wink, a touch of hands, all of these sweet things were what left in my memory.
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Junior year summer, we had a little clique of four. J proposed to have an excursion to Huashan.
We started in the late afternoon and the plan was to see the sunrise.
Except the next morning was very cloudy. Disappointed, we started heading down.
I was the leading the pack.
On the last of these steep step, I was on the plank already; an ouch from C.
Simple reflex. Within a split of second, I fell to the plank. Left hand on the inside of the plank and right hand grabbed C's arm.
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Every body yell hold on. Some guys tried to help to no avail. There was no space.
I yelled hold on, grab tight. Her voice is low, eyes were teary, murmuring, don't let me go.
Sweat came out; it creeped from the back in the beginning then all the way to the hands.
A piece of red sleeve was the only thing in the hand.
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It escaped me how I got to the motel, although I wanted to jump down to go with her at one moment.
__________________________My story__________________________________
Guilty; because I proposed for the excursion.
I went to the police station and told what happened. Then made a lot of phone calls to get thru to W and C's families. Hard to be the messenger when the news was not a good one.
It didn't take too long for the police to recover the body in the late afternoon. Half a dozen people fell each year at the same location; they knew exactly where to find them.
The next morning, both W's father and C's uncle came to meet us. Broken hearts. Some are more broken. Her mother got hospitalized at the news.
At the night in the hotel room, we were sitting there silently. W murmured to carry her to the family graveyard, and his father shook his head. There was not for negotiation.
The two middle aged men from the two families talked in business tone. The final decision was W's father would pay for all the expenses.
As per local custom of central China, they needed to find a dead husband for C, so she would form a family in the other world. Otherwise she would be lonely. This was normally done by an agreement of the two families without consent of the deceased ones, then the tomb of the previously deceased one was reopen and the coffin of the newly deceased was buried side by side.
This had to be done fast as these days were hot. Fortunately or unfortunately, 20 mile to the north, a young bachelor died of car accident several weeks ago. His family felt so happy that they could find a wife for him.
There was a brief ceremony in the village of the young dead guy. We were told to keep off. But W insisted and I had to go with him.
W could not suppress this sobbing at one point. then we were pushed out. "we are having a marriage ceremony; your irrelevant guys messed up the merry air "
There are things that it is hard to let go. I know that is what happening with W, as shown by the combination: the wife is a much smaller version of C, and the muscles of arms twice as large as these of a regular man.
But life doesn't give a chance to let you relive part of it.
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