Messages

121

General Questions and Answers / Re: Question on the alignment of Fermi energy

« on: January 16, 2011, 15:57 »

Maybe I didn't express clearly,  i optimize the isolated molecule in Dmol3, and get the fermi level. When i rotate the isolate molecule along the X axis and then optimize it, i will get the same fermi level.

122

General Questions and Answers / Question on the alignment of Fermi energy

« on: January 13, 2011, 17:07 »

Dear everyone
    i want to study the transport properties in molecular devices with different orientation, When the  molecule is contacted by two Au (111) electrodes in different orientation, the Fermi energy of isolated molecule can be set to the electrochemical potential of the electrode. In the process, our calculation indicates that there is a tiny charge transfer between the gold electrode and the molecules. For one orientation, the charge transfer is 0.22e, for another is 0.07e. The Fermi energy of the isolated molecule in different orientation is the same. why the charge transfer is different in the process of alignment?

123

General Questions and Answers / Re: question on optimizing the two probe

« on: December 20, 2010, 18:12 »

thanks a lot

124

General Questions and Answers / question on optimizing the two probe

« on: December 17, 2010, 15:42 »

when i put the molecule into the electrode, how to confirm the distance between the molecule and the electrode?
if i want to  optimize the distance between the surface layer and the molecule

thank you
 

125

General Questions and Answers / Re: qusetions on temperature

« on: December 12, 2010, 15:49 »

thank you very much 

126

General Questions and Answers / Re: question on convergence

« on: December 11, 2010, 12:49 »

thank you 

127

General Questions and Answers / qusetions on temperature

« on: December 11, 2010, 10:40 »

i calculate the two probe system, in the low bias voltage area,between -0.8V to 0.8V, it is convergence,and i use the temperature 300k.
but from -0.9V to 1.5V, it isn't convergence, so i increase the temperature to 1000k, it converges. will this affact the results much? i mean the transmission spectrum,I-V, conductance.
thank you

128

General Questions and Answers / question on convergence

« on: December 11, 2010, 10:29 »

hello everyone
   the distance between the molecular and the electrode will infect the convergence ,is it right??
   if the distance is too short, it is hard to converge???

129

General Questions and Answers / Re: questions about the convergence

« on: December 9, 2010, 00:54 »

i'm waiting for you
 :)thank you  very much

130

General Questions and Answers / transmission spectrum and transmission coefficients

« on: December 8, 2010, 17:10 »

i'm a rookie
canyou tell me the diffenence between the transmission spectrum and transmission coefficients
i think the transmission coefficients is calculated in a fixed energy (such as E=0),but the transmission spectrum is calculated in a energy range(such as -2ev to 2ev),if i choose the energy range from 0ev to 0ev. at this time, are they equal to each other??
 thank you

131

General Questions and Answers / Re: Can anyone tell me the reasons?

« on: December 8, 2010, 15:55 »

i 've the same problem can you tell me how to deal with it thank you

132

General Questions and Answers / Re: The computation failed to converge when the negative bias was applied

« on: December 8, 2010, 15:46 »

for my system, when i use k points 3*3*100 for convergence it is successful from -2.0V to 2.0v. but when i change the K points to 5*5*100 others are the same  ,it converges well in positive bias voltage but in negative, it doesn't converge at all.  http://quantumwise.com/forum/index.php?topic=888.0
what should i do?

133

General Questions and Answers / Re: questions about the convergence

« on: December 8, 2010, 15:02 »

thank you very much Nordland
if i insiste on the 2008.10 canyou give me some advices on the problem
     best wishes

134

General Questions and Answers / questions about the convergence

« on: December 7, 2010, 17:56 »

Dear blom:
     i've some questions about the convergence
① in my two probe system,when the bias voltage is set at -0.9V, it doesn't converge at all,  but in 0.9V it works well. why? because of the asymmetry of the molecular or the position of the molecular in the two probe?              
② i increase the temperature of the electrode from 300k to 1000k in the -0.9V,but it doesn't work!! what should i do ?
 the electrode iteration mixing parameters are set as follows:
     iterationMixingParameters
    algorithm = IterationMixing.Pulay,
    diagonal_mixing_parameter = 0.01,
    quantity = IterationMixing.Hamiltonian,
    history_steps = 15
and the k point is 5*5*100,

135

General Questions and Answers / Re: Some doubt about MPSH result

« on: October 8, 2010, 04:59 »

in the new vension 2010, atk can calculate the occupancies for Twoprobe Projected Hamiltonian energy spectrum, i want to ask about how to get the HOMO and LUMO?  is that the HOMO as the last negative energy and the LUMO as the first positive energy?  or  identify the HOMO-LUMO according to the occupancies?