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General Questions and Answers / fixed spin
« on: June 2, 2009, 13:59 »
Is there any way to utilize the fixed spin tag for periodic calculations?
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General Questions and Answers / Small Transmission Coefficients and Low Current
« on: April 10, 2009, 15:09 »
Hi all,
I am calculating a 1D structure and seeing small transmission coeffients such that the resulting current values are at microAmpere range at finite biases. I first checked charge but there is no charge missing. There are approximately 51.60272 spin-up charges and 52.72461 spin-down charges in the central region at 1V (# sc 47 : q = 104.32771 e Etot = -397.37066 Ry dRho = 9.6462E-04 dEtot = 3.2366E-04 Ry). Then I tought that it might depend on number of buffer layers, so I repeated the calculation with 10-10, 20-20 and 40-40 buffer layers. Unfortunately this caused another problem. I saw that transmission properties of the device changes depending on the number of buffer layers. This is unphysical. At last I've checked the voltage drop (by choosing electrode constraint as Density Matrix) and saw no abrupt change in the potential. Then I conclude that the scattering of the electrons from the contact cannot be the cause of this small transmission coefficients.
Any new ideas?
ps. Plots of the voltage drop for the spin-up and spin-down electrons and transmission spectrums at 1V are attached successively (due to size limitations I attached them seperately).
I am calculating a 1D structure and seeing small transmission coeffients such that the resulting current values are at microAmpere range at finite biases. I first checked charge but there is no charge missing. There are approximately 51.60272 spin-up charges and 52.72461 spin-down charges in the central region at 1V (# sc 47 : q = 104.32771 e Etot = -397.37066 Ry dRho = 9.6462E-04 dEtot = 3.2366E-04 Ry). Then I tought that it might depend on number of buffer layers, so I repeated the calculation with 10-10, 20-20 and 40-40 buffer layers. Unfortunately this caused another problem. I saw that transmission properties of the device changes depending on the number of buffer layers. This is unphysical. At last I've checked the voltage drop (by choosing electrode constraint as Density Matrix) and saw no abrupt change in the potential. Then I conclude that the scattering of the electrons from the contact cannot be the cause of this small transmission coefficients.
Any new ideas?
ps. Plots of the voltage drop for the spin-up and spin-down electrons and transmission spectrums at 1V are attached successively (due to size limitations I attached them seperately).
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General Questions and Answers / How to initialize an optimization calculation using elec.dens. of another calc.?
« on: February 12, 2009, 15:35 »
I want to use relaxed atomic positions and electron density of a previously converged calculation as an initial guess to an optimization calculation. However, 'initial_calculation' argument is only avaible for executeSelfConsistentCalculation not for calculateOptimizedAtomicGeometry. Is there another way?
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