Abstract
Since Sayre's equation is the basis of some direct-methods procedures, the applicability of Sayre's equation has been tested in various circumstances. When a structure contains a heavy atom, it is found that Sayre's equation does not hold well, which is expected since the condition of equal resolved atoms does not apply. However, what is not expected is that with a heavy atom present the equation actually holds better at low resolution than at high resolution. The cause of this apparent anomaly is discussed and it is shown that there exists a modified Sayre's equation which holds far better in the presence of one kind of heavy atom in a structure. While this modified equation is difficult to use, it is possible that it may find application if the full power of modern computer technology is utilized.
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Schedule a callMore From: Acta Crystallographica Section A Foundations of Crystallography
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