[Pw_forum] Sawlike potential - clarification

[Konstantin Kudin]

 Hi all,

 "INPUT_PW" says the following on adding sawlike potential:

"emaxpos        REAL ( default = 0.5D0 )
               Position of the maximum of the sawlike potential within
the 
               unit cell ( 0 < emaxpos < 1 )

eopreg         REAL( default = 0.1D0 )
               Part of the unit cell where the sawlike potential
decreases.
               ( 0 < eopreg < 1 )

eamp           REAL ( default = 0.001 a.u. )
               Amplitude of the electric field (in a.u.) 
	       ( 1 a.u. = 51.44 10^10 V/m )"

 What does "Part of the unit cell where the sawlike potential
decreases" really mean? Is that where the sawlike potential is at its
minimum?

 Also, are there any drawbacks in using a highly asymmetric saw tooth?
For example, is it a good idea to have a narrow region where the
potential drops from highest to lowest, and then a wide region where it
increases?

 If asymmetric saw tooth is OK, then what does "eamp" set? Is it the
field in the longer part of the tooth, or in the shorter one?

 Thanks in advance!
 Kostya



		
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