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[求助]
為什么我的GSAS精修Rp Rwp如此的小呢?
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大家好!我用GSAS精修粉末XRD得到的Rp=0.5%,Rwp=0.63%,chi2=0.1444;為什么我Rp和Rwp的值比別人的小一個數(shù)量級呢?(順便問一下 GSAS liveplot中的wRp是不是就是Rwp呢?)大牛們精修的值不可能比我小啊,精修的圖形也還行啊見附圖(說明一下,圖中扣除了一些非晶背底)請大俠賜教為什么? 部分精修圖 |
GSAS結(jié)構(gòu)精修 |
至尊木蟲 (著名寫手)
至尊木蟲 (著名寫手)
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If the background has been subtracted, yi(obs) is the net intensity after subtraction, but if the background is refined, yi(obs) [and yi(calc)] is likely to include the background contribution. In the latter case, a high background will automatically produce a low Rwp value, because a significant part of the intensity is accounted for by the background function. Thus, the comparison of profile R values from different kinds of powder diffraction experiments can be extremely misleading. For example, Rwp for neutron TOF data are often quite small (e.g. a few %), while those for laboratory X-ray data are larger (e.g. ~10%). 從這段話里可以知道你的Rwp為什么那么低的原因是你背底很高 |
鐵桿木蟲 (知名作家)
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木蟲 (小有名氣)
至尊木蟲 (著名寫手)
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你這個太小了0.144,你看看下面文獻(xiàn)的說明,希望對你有幫助。 J. Appl. Cryst. (1999). 32, 36-50 chi2 is also quoted quite often in the literature, should approach 1. If the data have been `over-collected' (i.e. errors are no longer dominated by counting statistics), Rexp will be very small and chi2 for a fully refinned structure much larger than 1. Conversely, if the data have been `under-collected' (i.e. collected too quickly), Rexp will be large and chi2 could be less than 1. Strange chi2 values can also arise from data for which the e.s.d.'s of the counts have been incorrectly calculated (e.g. counts given as counts per second are assumed to be the absolute counts). |
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