Mario Tribaudino, Piera Benna, and Emiliano Bruno
Structural variations induced by thermal treatment in lead feldspar (PbAl₂Si₂O₈)    159

TABLE 3. T-O bond lengths (Â) and Qod value for lead feldspars

								
            	PbFL1h		PbFL16h		PbFL64h		PbFH136h
				
T1(0)-OA(1)	1.636(6)	1.665(13)	1.654(12)	1.688(9)
T1(0)-OB(0)	1.632(7)	1.609(15)	1.637(12)	1.649(8)
T1(0)-OC(0)	1.615(7)	1.622(11)	1.619(10)	1.643(5)
T1(0)-OD(0)	1.626(8)	1.626(13)	1.635(13)	1.664(7)
Mean        	1.627		1.631		1.636		1.661
				
T1(z)-OA(1)	1.760(7)	1.725(14)	1.754(12)	1.717(9)
T1(z)-OB(z)	1.722(7)	1.698(15)	1.698(12)	1.698(8)
T1(z)-OC(z)	1.727(7)	1.728(11)	1.724(10)	1.712(5)
T1(z)-OD(z)	1.773(8)	1.747(13)	1.737(12)	1.722(8)
Mean        	1.746		1.725		1.728		1.712
				
T2(0)-OA(2)	1.751(6)	1.735(11)	1.741(9)	1.715(5)
T2(0)-OB(0)	1.723(7)	1.725(15)	1.699(12)	1.689(9)
T2(0)-OC(0)	1.708(8)	1.704(14)	1.731(12)	1.706(7)
T2(0)-OD(0)	1.739(7)	1.728(12)	1.717(13)	1.704(8)
Mean        	1.730		1.723		1.722		1.704

T2(z)-OA(2)	1.646(6)	1.642(11)	1.637(8)	1.655(5)
T2(z)-OB(z)	1.601(7)	1.621(15)	1.622(12)	1.636(8)
T2(z)-OC(z)	1.612(7)	1.602(13)	1.603(12)	1.622(7)
T2(z)-OD(z)	1.620(7)	1.625(12)	1.643(13)	1.650(8)
Mean        	1.620		1.623		1.626		1.641
				
Qod         	0.85		0.72		0.70		0.42

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TABLE 4. Pb-O bond lengths (Â) for lead feldspars (non-split model)

						
            	PbFL		PbFL1h		PbFL16h		PbFL64h		PbFH136h	PbFH*
						
Pb - OA(1)	2.753(5)	2.763(9)	2.771 (12)	2.744(11)	2.743(5)	2.729(7)
Pb - OA(1)	2.657(5)	2.659(8)	2.660(12)	2.673(11)	2.691(5)	2.729(7)
Pb - OA(2)	2.465(5)	2.457(8)	2.481(9)	2.485(9)	2.491(4)	2.508(11)
Pb - OB(0)	2.806(5)	2.808(8)	2.830(11)	2.836(11)	2.880(6)	2.918(8)
Pb - OB(z)	3.121(5)	3.113(8)	3.078(11)	3.050(12)	3.017(6)	2.918(8)
Pb - OC(0)	3.346(5)	3.342(7)	3.289(11)	3.283(10)	3.230(5)	3.143(7)
Pb - OC(z)	3.000(5)	3.009(8)	3.028(11)	3.030(10)	3.083(5)	3.143(7)
Pb - OD(0)	2.784(6)	2.787(8)	2.802(12)	2.803(12)	2.783(7)	2.785(7)
Pb - OD(z)	2.592(6)	2.601(7)	2.666(12)	2.659(11)	2.698(7)	2.785(7)
						
Note: PbFL and PbFH : Benna et al. (1996). *The refinement was performed according to s.g. C2/m.