Powder Diffraction Project

Refinement with the group P2₁/n

Step	Circles	R_wp	Scale (refined)	Other parameters refined (values after the refinement)
1.	4	23.289	2.6513	-
2.	5	20.212	2.7463	CELL PARAMETERS (a, b, c) = 6.928028 8.414592 5.369398 ZEROPOINT = .07538
3.	3	19.831	2.6555	PEAK SHAPE PARAMETERS Gam0 = .618869 Gam1 = -.020061 Gam2 = .000092
4.	6	15.302	2.8196	HALFWIDTH PARAMETERS U = .049408 V = -.011639 W = .174270 PEAK SHAPE PARAMETERS Gam0 = .211182 Gam1 = -.003261 Gam2 = .000034
5.	6	14.612	2.8373	CELL PARAMETERS (a, b, c) = 6.928234 8.418896 5.370432 ZEROPOINT = .08877 HALFWIDTH PARAMETERS U = .014558 V = .034213 W = .161829 PEAK SHAPE PARAMETERS Gam0 = .255794 Gam1 = -.004415 Gam2 = .000043
6.	6	14.574	2.8329	(Pb (z): 0.250->0.251 )* PB (x, y, z) .16851 .18984 .25448
7.	2	14.340	2.8354	(S (z): 0.750->0.751 )* S (x, y, z) .18217 .43376 .75889
8.	5	14.274	2.8389	O3 (x, y, z) .30419 .41355 .98018 O4 (x, y, z) .31079 .42333 .53119
9.	6	14.137	2.8401	(O1 (z): 0.750->0.751 )* (O2 (z): 0.750->0.751 )* O1 (x, y, z) .09544 .59219 .75835 O2 (x, y, z) .03861 .30720 .76648
10.	2	14.120	2.8491	PB (x, y, z) .16821 .18964 .25657 S (x, y, z) .18125 .43327 .75803 O1 (x, y, z) .09585 .59221 .76035 O2 (x, y, z) .03844 .30721 .76623 O3 (x, y, z) .30107 .41569 .97714 O4 (x, y, z) .31418 .42149 .52840
11.	4	14.039	2.7383	PB (B) .4492 S (B) .5079 O1 (B) .5629 O2 (B) .5384 O3 (B) .8042 O4 (B) .1169
12.	4	14.013	2.739	HALFWIDTH PARAMETERS U = .004166 V = .038862 W = .164550 PEAK SHAPE PARAMETERS Gam0 = .287516 Gam1 = -.006996 Gam2 = .000065
13.	7	9.186	2.7922	CELL PARAMETERS (a, b, c, beta) = 6.928361 8.418925 5.371339 89.781940 ZEROPOINT = .09269 HALFWIDTH PARAMETERS U = .034898 V = -.122596 W = .208687 PEAK SHAPE PARAMETERS Gam0 = .232218 Gam1 = -.004155 Gam2 = .000047
14.	7	6.031	2.8111	PB (x, y, z) .16825 .18924 .24266 S (x, y, z) .18259 .43412 .74989 O1 (x, y, z) .09395 .59257 .73961 O2 (x, y, z) .04069 .30560 .75577 O3 (x, y, z) .30707 .42113 .97259 O4 (x, y, z) .30862 .41610 .52509 CELL PARAMETERS (a, b, c, beta) = 6.928289 8.418904 5.371289 89.762500 ZEROPOINT = .09133 HALFWIDTH PARAMETERS U = .044302 V = -.141457 W = .210029 PEAK SHAPE PARAMETERS Gam0 = .225196 Gam1 = -.002833 Gam2 = .000030
15.	3	6.028	2.8118	CELL PARAMETERS (a, b, c, beta) = 6.928291 8.418905 5.371289 89.762470 ZEROPOINT = .09134 HALFWIDTH PARAMETERS U = .044195 V = -.141266 W = .209958 PEAK SHAPE PARAMETERS Gam0 = .226285 Gam1 = -.002858 Gam2 = .000030
16.	4	5.550	2.7108	PB (B) .2229 S (B) .3650 O1 (B) .5699 O2 (B) .4773 O3 (B) .3648 O4 (B) .4567 CELL PARAMETERS (a, b, c, beta) = 6.928273 8.418887 5.371424 89.761760 ZEROPOINT = .09188
17.	4	5.517	2.7092	CELL PARAMETERS (a, b, c, beta) = 6.928288 8.418886 5.371415 89.761730 ZEROPOINT = .09185 HALFWIDTH PARAMETERS U = .042708 V = -.140985 W = .211309 PEAK SHAPE PARAMETERS Gam0 = .184137 Gam1 = -.002943 Gam2 = .000037
18.	4	5.472	2.6868	PB (x, y, z, B) .16853 .18925 .24197 .1872 S (x, y, z, B) .18338 .43415 .74611 .3349 O1 (x, y, z, B) .09380 .59239 .73953 .5742 O2 (x, y, z, B) .04093 .30548 .75559 .4460 O3 (x, y, z, B) .30674 .42108 .97282 .3061 O4 (x, y, z, B) .30856 .41582 .52527 .4724 CELL PARAMETERS (a, b, c, beta) = 6.928273 8.418869 5.371417 89.761760 ZEROPOINT = .09188 HALFWIDTH PARAMETERS U = .041965 V = -.139866 W = .211208 PEAK SHAPE PARAMETERS Gam0 = .175894 Gam1 = -.003058 Gam2 = .000039

* The way how previous symmetry was broken - special positions coordinates (z = 1/4, z = 3/4) changed by a small amount (0.001).

Parameters for this structure are given in the next two tables:

Atom	Atom	Distance (in angstroms)
S	O1	1.470
S	O2	1.466
S	O3	1.495
S	O4	1.475

Bond lengths

Atom	Atom	Atom	Angle (in degrees)
O1	S	O2	112.7
O1	S	O3	109.2
O1	S	O4	108.8
O2	S	O3	107.7
O2	S	O4	110.1
O3	S	O4	108.1

Bond angles

and the final plot is:

Final Plot

The results obtained with the group P2₁/n are better then those obtained with P2₁/a by 20% in terms of R-factor value, and the former seem to be a better choice for this structure.

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Student: Siniūa Prokic