題組內容

6. An unknown metal sample X (single phase, with no obvious segregation) was measured by powder XRD using Cu Kα radiation (λ=1.5406 Å). The observed peaks are listed below.The observed peaks are listed below (backgroundsubtracted). Detection limit: reflections with a relative intensity < 0.5% are considered not observable. (10%)

Here are the equations/information you may need below:
2dsin0=nλ

Simple cubic: all (hkl) reflections are allowed.
Body-centered cubic (bcc): reflections are allowed only when h+k+l is even.
Face-centered cubic (fcc): reflections are allowed only when h,k,l are all odd or all even.
Answer the following questions:

c) If a very weak peak appears at 2θ=30.5° (relative intensity 1%), how would you determine whether it arises from a second/impure phase, or it still corresponds to a single phase? (10%)