[Smeagol-discuss] How to avoid the noise in the Transmission?

[Barraza-lopez, Salvador]

Some times during calculation of transmission coefficients you get the following message: 
no. of left channels .ne. number of right channels 

Look at your output and seek any warning message like the one just mentioned. 

If you are indeed getting a couple of these messages, the associated transmission at these energy points is skipped; it will not be written to file. You'll miss it on the TRC file. It means there's some singularity 
at those energies and the self-energies are not computed. If they are skipped in the file it'll appear as a depression at isolated points on the TRC plot. 

Suggestions, in case you do see the warning message I mention (or other similar) in your output. 

(1) Try increasing your Delta parameter, say by one order of magnitude or so. This will perhaps help avoiding singularities on the construction of the self energies for transmission purposes. 

(2) Is you calculation with Gamma point only? If so, you could increase the number of k-points; that'll average the noise out. 

(3) Other thing I'd suggest is changing the number of energy points in your TRC file. You may very probably miss these points (and get other similar ones in other energy regions probably). 

Cheers, 
-Salvador. 


----- Original Message ----- 
From: "Wang Qinjing" <041019019 at fudan.edu.cn> 
To: smeagol-discuss at lists.tchpc.tcd.ie 
Sent: Thursday, February 26, 2009 3:47:51 AM GMT -05:00 US/Canada Eastern 
Subject: [Smeagol-discuss] How to avoid the noise in the Transmission? 



Dear all: 

I've sent this email before, unfortunately it is hold because the the attched file is over the limit of 40 KB. I resend the email now: 


Dear SMEAGOL users: 

I am calculating the transmission of a lead-molecular-lead system by SMEAGOL and get the relation of the transmission coefficient and the energy from the output file *.TRC. The picture of TRC versus energy is also sent as attachment. 

My problem is, are the two peaks at about -0.12 Ry and -0.15 Ry, as pointed out by two red arrows, the noise in the transmission? It seems there are not any physical meanings. Are they really noise? If they are noise, how can I avoid them? 

Thank you all in advance 

Wang Qinjing 

===================================== 
王秦镜 复旦大学物理系研究生 
Wang Qinjing, Postgraduated students 
Physics Department, Fudan University 
===================================== 
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