Simulation of magnetic resonance static powder lineshapes: A quantitative assessment of spherical codes
Simulation of magnetic resonance static powder lineshapes: A quantitative assessment of spherical codes
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磁共振静态粉末线形模拟：球形代码的定量评估
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发表时间：
1999
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通讯作者：
Alessandro Ponti
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作者：
Alessandro Ponti
磁共振静态粉末光谱的模拟是通过(可能是加权的)计算的单晶谱的总和来执行的，这些单晶谱是针对相对于磁相互作用的主轴的不同取向的外场计算的。许多可用的方法在积分点(即方向)和权重的选择上不同，其集合被称为球面代码。最大限度地减少良好模拟所需的积分点的数量一直是人们的兴趣。忽略积分点之间可能的跃迁频率和强度的内插，我们将注意力转向球码本身的效率。为此，提出了一种无偏的定量方法来评估它们在模拟磁共振静态粉末光谱方面的效率。为了实现公正的判断，程序的设计仔细考虑了以下几点：准确参考光谱的选择；优点系数的准确定义；积分点数目的扩展范围；效率的方位依赖性。所提出的方法已被应用于包含23个球形代码的集合。结果发现，大多数代码的执行情况都非常相似。螺旋是最有效的程序，而蒙特卡罗和“排斥”程序显示了最好的旋转不变性的模拟线形相对于球面代码的取向。版权所有1999年学术出版社。
Simulation of magnetic resonance static powder spectra is performed by a (possibly weighted) summation of single-crystal spectra computed for different orientations of the external field with respect to the principal axes of the magnetic interactions. The many available methods differ in the choice of the integration points (i. e., orientations) and weights, the set of which is called spherical code. There is continuing interest in minimizing the number of integration points necessary to a good simulation. Neglecting the possible interpolation of transition frequencies and intensities between integration points, we turn our attention to the efficiency of spherical codes themselves. To this end, an unbiased quantitative procedure to assess their efficiency in simulating magnetic resonance static powder spectra is proposed. To achieve an impartial judgement, the procedure has been designed by carefully taking into consideration the following points: choice of exact reference spectra; accurate definition of the merit figures; extended range of number of integration points; orientation dependence of the efficiency. The proposed procedure has been applied to an inclusive set of 23 spherical codes. It was found that most codes perform rather similarly. SPIRAL is the most efficient code, whereas Monte Carlo and "repulsive" codes show the best rotational invariance of the simulated lineshape with respect to the orientation of the spherical code. Copyright 1999 Academic Press.