[Pw_forum] The top of VB in total DOS differ from one in projection DOS

[idoldog]

Dear PWSCF user,

I do DOS calculations of SrTiO3 using code pw.x, dos.x, projwfc.x, and get a strange DOS. 

The projection DOS shows that top of valence band consists of La 5p and O 2p. But I find the top of valence band in total DOS is different from the one in projection DOS of La 5p and O 2p. I mark the disagreement using two dotted lines in the first picture. 

I check the data of the three graph, and plot them in the same picture. There are some negative value points. I mark them in the second picture. In my mind, DOS might mean electron number per eV. I don't know what the negative value mean. 

I guess that these negative value points result in the disagreement between total DOS and projection DOS.  If In a same energy, the point in same projection DOS (such as Ti) is negative value, and the others (La 5p and O 2p for example) are positive value, their sum might be zero or negative value. So the top of VB in total DOS differ from one in projection DOS.

All DOS. : http://pic.emuch.net/200903/07/7bb56af4f95135d74607726506ed8ded.jpg
negative point in DOS. :http://pic.emuch.net/200903/07/eb8445e98a9516b05b13dc28fd90259c.jpg

I want to know where my mistakes are and how to solve them. 

I'm looking forward to your help.

All best.
 				
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李飞  硕士研究生  

2009-3-07

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南开大学化学学院

天津市南开区卫津路94号

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