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Triclinic crystal cell parameters

Triclinic crystal cell  in 3-d is described by cell edge lengthes, a, b, c, and associated angles between edges, alpha, beta, and gamma, as shown in the plot.

Code Block
                *----------*
               / \        / \
              /   \      /   \
             /     \ gamma    \
            /       *----------*
           /       /  /       /
          /alpha  /  /       /
         *-------/--*       c
          \     /    \beta /
           a   /      \   /
            \ /        \ /
             *-----b----*

As a starting point in this analysis we use parameters from previous study

Code Block
  a = 18.36 A
  b = 26.65 A
  c = 4.81 A
  alpha = 90.00 deg
  beta  = 90.00 deg
  gamma = 102.83 deg

See: Crystal structure, Bravais lattice, Crystal system, Primitive cell, Lattice constant

3-d space primitive vectors

Crystal cell parameters can be transformed to 3-d primitive vectors

Code Block
  a1 = (18.36, 0.0, 0.0)
  a2 = (5.917873795354449, 25.984635262829016, 0.0)
  a3 = (0.0, 0.0, 4.81)

Reciprocal space primitive vectors

See: Reciprocal lattice, Surface diffraction, Miller index3-d primitive vectors can be converted in reciprocal space primitive vectors

Code Block
  b1 = [ 0.05446623  0.01240442  0.        ]
  b2 = [ 0.          0.03848428  0.        ]
  b3 = [ 0.          0.          0.20790021]

 See: Reciprocal lattice, Surface diffraction, Miller index

Table of lattice nodes sorted by radius

Lattice nodes in reciprocal space can be evaluated from primitive vectors and associated Muller indexes h,k,l. Lattice nodes ordered by ascending R(h,k,l) - distance between (h,k,l) and (0,0,0) points, is presented in table

Code Block
2-d case                3-d case
( h, k) R(h,k)[1/A]     ( h, k, l) R(h,k,l)[1/A]
___________________     ________________________
( 0, 0) 0.0000          ( 0, 0, 0) 0.0000
( 0, 1) 0.0385          ( 0, 1, 0) 0.0385
( 1, 0) 0.0559          ( 1, 0, 0) 0.0559
(-1, 1) 0.0604          (-1, 1, 0) 0.0604
( 1, 1) 0.0745          ( 1, 1, 0) 0.0745
( 0, 2) 0.0770          ( 0, 2, 0) 0.0770
(-1, 2) 0.0845          (-1, 2, 0) 0.0845
( 1, 2) 0.1047          ( 1, 2, 0) 0.1047
(-2, 1) 0.1098          (-2, 1, 0) 0.1098
( 2, 0) 0.1117          ( 2, 0, 0) 0.1117
( 0, 3) 0.1155          ( 0, 3, 0) 0.1155
(-1, 3) 0.1166          (-1, 3, 0) 0.1166
(-2, 2) 0.1208          (-2, 2, 0) 0.1208
( 2, 1) 0.1260          ( 2, 1, 0) 0.1260
( 1, 3) 0.1390          ( 1, 3, 0) 0.1390
(-2, 3) 0.1417          (-2, 3, 0) 0.1417
( 2, 2) 0.1491          ( 2, 2, 0) 0.1491
(-1, 4) 0.1517          (-1, 4, 0) 0.1517
( 0, 4) 0.1539          ( 0, 4, 0) 0.1539
(-3, 1) 0.1634          (-3, 1, 0) 0.1634
( 3, 0) 0.1676          ( 3, 0, 0) 0.1676
(-3, 2) 0.1682          (-3, 2, 0) 0.1682
(-2, 4) 0.1689          (-2, 4, 0) 0.1689
( 1, 4) 0.1750          ( 1, 4, 0) 0.1750
( 2, 3) 0.1776          ( 2, 3, 0) 0.1776
( 3, 1) 0.1801          ( 3, 1, 0) 0.1801
(-3, 3) 0.1812          (-3, 3, 0) 0.1812
(-1, 5) 0.1881          (-1, 5, 0) 0.1881
( 0, 5) 0.1924          ( 0, 5, 0) 0.1924
( 3, 2) 0.1993          ( 3, 2, 0) 0.1993
(-2, 5) 0.1999          (-2, 5, 0) 0.1999
(-3, 4) 0.2008          (-3, 4, 0) 0.2008
( 2, 4) 0.2093          ( 0, 0, 1) 0.2079 1st contributing index with l=1
( 1, 5) 0.2119          ( 2, 4, 0) 0.2093
(-4, 1) 0.2181          ( 0, 1, 1) 0.2114
(-4, 2) 0.2196          ( 1, 5, 0) 0.2119
( 4, 0) 0.2234          ( 1, 0, 1) 0.2153
( 3, 3) 0.2236          (-1, 1, 1) 0.2165
(-3, 5) 0.2254          (-4, 1, 0) 0.2181
(-4, 3) 0.2276          (-4, 2, 0) 0.2196
( 4, 1) 0.2350          ( 1, 1, 1) 0.2209
(-4, 4) 0.2416          ( 0, 2, 1) 0.2217
( 2, 5) 0.2430          ( 4, 0, 0) 0.2234
( 3, 4) 0.2515          ( 3, 3, 0) 0.2236
( 4, 2) 0.2520          (-1, 2, 1) 0.2244
(-4, 5) 0.2605          (-3, 5, 0) 0.2254
(-5, 2) 0.2727          (-4, 3, 0) 0.2276
( 4, 3) 0.2733          ( 1, 2, 1) 0.2328
(-5, 1) 0.2733          ( 4, 1, 0) 0.2350
(-5, 3) 0.2775          (-2, 1, 1) 0.2351
( 5, 0) 0.2793          ( 2, 0, 1) 0.2360
( 3, 5) 0.2818          ( 0, 3, 1) 0.2378
(-5, 4) 0.2874          (-1, 3, 1) 0.2383
( 5, 1) 0.2903          (-2, 2, 1) 0.2404
( 4, 4) 0.2982          (-4, 4, 0) 0.2416
(-5, 5) 0.3019          ( 2, 5, 0) 0.2430
( 5, 2) 0.3057          ( 2, 1, 1) 0.2431
( 5, 3) 0.3251          ( 1, 3, 1) 0.2501
( 4, 5) 0.3257          ( 3, 4, 0) 0.2515
( 5, 4) 0.3476          (-2, 3, 1) 0.2516
( 5, 5) 0.3727          ( 4, 2, 0) 0.2520

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This makes event selection more complicated and in result the same matching algorithm finds 4× less peaks. Image Added

 

 

 

 

References

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