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zhouweixia

铁杆木虫 (正式写手)

[求助] 求助键长进位的问题

在生成的cif文件中,键长的不确定标准偏差大于十时,如何通过进位,使得其小于十,进位规则是什么。比如,Cu-Cu键长为2.5927(14),那么要使得括号内的值小于十,咋么进位?希望各位高手给我支支招,谢谢!
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wormma

木虫 (正式写手)

One for All, All for One

【答案】应助回帖

★ ★
帝夫(金币+2, CMEI+1): 很好!授予CMEI一枚,欢迎继续关注晶体版! 2011-12-16 14:57:32
找到了“晶体学会的规定”。按作者自己的说法,只是‘recommadation'.如果想在误差中保留1位有效数字,仍然是符合规定的,只是舍入误差稍大。下面是原文,供查阅。
12. The numerical value of an estimate y and its
standard uncertainty u(y) should not be reported with an
excessive number of digits. However, y should be quoted
with sufficient accuracy to minimize the effect of roundoff
error* in subsequent calculations. In order to limit the
round-off error of y (denoted by e) to 25% of u(y), u(y)
should be quoted to two significant digits in the range 10
to 19, implying that corresponding digits also be quoted
for y, and to one significant digit in the range 2 to 9. In
general, uncertainties should be rounded up rather than
to the nearest digit. For example, a bond distance of
1.542 49/~ with a s.u. of 0.015 32/~ should be reported
as 1.542 (16)/~ (e = 3%), and one of 2.163 52A with
a s.u. of 0.004 81/~ should be reported as 2.164 (5)/~
(e = 10%). Correlation coefficients should normally be
quoted with two significant figures unless their absolute
value is close to the value of 1.0, in which case three
significant figures should be used.
OneforAll,AllforOne
15楼2011-12-16 12:53:02
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wormma

木虫 (正式写手)

One for All, All for One

【答案】应助回帖


感谢参与,应助指数 +1
lijunjie84(金币+1): 谢谢应助! 2011-12-14 12:40:23
这个要理解其含义,2.5927(14)表示2.5927+-0.0014,第一个可疑数字是千分位的1,故写为2.592(1)
OneforAll,AllforOne
2楼2011-12-14 09:46:53
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zhouweixia

铁杆木虫 (正式写手)

引用回帖:
2楼: Originally posted by wormma at 2011-12-14 09:46:53:
这个要理解其含义,2.5927(14)表示2.5927+-0.0014,第一个可疑数字是千分位的1,故写为2.592(1)

如果是(15)以上是不是要进位为2.592(2)?
进位时,括号前的数字奇偶性是否对进位有影响,比如2.5927(15)和2.5928(15)以及2.5928(14)该如何进位?谢谢!
3楼2011-12-14 10:22:05
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wormma

木虫 (正式写手)

One for All, All for One

【答案】应助回帖

引用回帖:
3楼: Originally posted by zhouweixia at 2011-12-14 10:22:05:
如果是(15)以上是不是要进位为2.592(2)?
进位时,括号前的数字奇偶性是否对进位有影响,比如2.5927(15)和2.5928(15)以及2.5928(14)该如何进位?谢谢!

不是,2.5927(15)-->2.592(1)
         2.5928(15)-->2.592(1)
         2.5928(14)-->2.592(1)
OneforAll,AllforOne
4楼2011-12-14 11:37:53
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