应《网络安全法》要求，自2017年10月1日起，未进行实名认证将不得使用互联网跟帖服务。为保障您的帐号能够正常使用，请尽快对帐号进行手机号验证，感谢您的理解与支持！

24小时热门版块排行榜    

小木虫论坛-学术科研互动平台 » 材料区 » 晶体 » 基础理论 » ((sinθ)/λ)max, A–1 在cif 中可以找到吗？ 代表什么值？
31/1返回列表
查看: 1211  |  回复: 2
只看楼主 @他人 存档 新回复提醒 (忽略) 收藏    在APP中查看

1987lengxin

银虫 (正式写手)

[求助] ((sinθ)/λ)max, A–1 在cif 中可以找到吗？ 代表什么值？

哪个大侠知道晶体数据 ((sinθ)/λ)max, A–1 在哪可以找到？代表什么意思？

[ Last edited by 1987lengxin on 2011-7-9 at 10:56 ]
回复此楼

» 收录本帖的淘帖专辑推荐

单晶解析

» 猜你喜欢

» 本主题相关价值贴推荐，对您同样有帮助:
点滴在心间
1楼 2011-07-03 13:29:19
已阅   回复此楼   关注TA 给TA发消息 送TA红花 TA的回帖

gy

至尊木虫 (正式写手)
S = SIN [_diffrn_reflns_theta_max] / _diffrn_radiation_wavelength
赞一下 回复此楼
2楼2013-07-16 15:02:10
已阅   回复此楼   关注TA 给TA发消息 送TA红花 TA的回帖

gy

至尊木虫 (正式写手)
http://journals.iucr.org/services/cif/checking/THETM_01.html

PROC-NAME: THETM01 Type_3

PURPOSE: To check that _diffrn_reflns_theta_max is greater than expected limits.

PROCEDURE:
CALCULATE

S = SIN [_diffrn_reflns_theta_max] / _diffrn_radiation_wavelength

TEST

IF S < 0.55 issue ALERT A
   "Alert A The value of sine(theta_max)/wavelength is less than 0.550"
< 0.575 issue ALERT B
   "Alert B The value of sine(theta_max)/wavelength is less than 0.575"
< 0.59 issue ALERT C
   "Alert C The value of sine(theta_max)/wavelength is less than 0.590"
The Commission on Journals has determined that setting the maximum sin(theta)/lambda for measurements to at least 0.6 is both optimal and achievable for most structural studies. The extent of the data not only affects the ratio of measurements to refined parameters and hence the accuracy of the atomic and geometric parameters, but also the reliability of the angular dependent terms, such as Uijs.
It is unlikely that any submitted CIF which contains the results of a data collection with a lower theta(max) will be accepted for publication unless there are exceptional circumstances. Old data claimed to have been collected when less stringent criteria were in place will not be excepted.

You should routinely set your diffractometer so that a theta(max) of 25 deg. for Mo radiation or 67 deg. for Cu radiation is the minimum that is achieved. If the crystal diffracts sufficiently well, it is strongly recommended that theta(max) is set to an even higher value.

It is understood that there may be little point in collecting background "noise" when a weakly diffracting crystal gives no detectable diffraction above theta values well below our required limit. In such a case, you should first ensure that you have conscientiously undertaken all possible steps to ensure that the experiment has been able to extract the best diffracting power from your sample. To this end, all of the following options should have been exhausted:

(a) The best possible crystal has been sought and utilised for the data collection. If the crystal was small or of poor quality, are you sure that a better or bigger one cannot be obtained? The chosen crystal may have been the best one in the batch, but had enough effort and patience really been expended in the crystallisation attempt? Often, lack of experience, impatience or unwillingness to try another crystallisation technique or solvent leads to the experimentalist abandoning crystallisation attempts before the optimal conditions have been found. Before you blame the crystal quality, be sure that you have convinced yourself that nothing further can be done in this direction.

(b) Use low temperature measurements to enhance the reflection intensities and the extent of the "observed" data.

(c) For organic compounds, try data collection with Cu radiation, which significantly enhances the reflection intensities.
赞一下 回复此楼
3楼2013-07-16 15:02:59
已阅   回复此楼   关注TA 给TA发消息 送TA红花 TA的回帖
相关版块跳转 我要订阅楼主 1987lengxin 的主题更新
31/1返回列表
普通表情 龙 兔 虎 猫
信息提示
关闭
请填处理意见
关闭