www.nextnano.com/documentation/tools/nextnano3/input_syntax/keywords/quantum-cluster.html 
Quantum cluster
For quantum solutions, you have to define quantum regions ($quantum-regions) and 
quantum clusters
on which certain quantum models ($quantum-model-electrons, 
$quantum-models-holes) are applied. 
As for the regions and current-regions, quantum-regions can be clustered. At least cluster number 1 has to be specified 
if the quantum mechanical properties have to be calculated at all. 
The syntax of the region-cluster, quantum-cluster, and current-cluster is 
very similar. 
For more info on specifiers see  $region-cluster,
$current-cluster. 
  
!-------------------------------------------------------------! 
$quantum-cluster                                    
optional  ! 
 cluster-number             
    integer       
    required  ! 
 region-numbers                
 integer_array      
required  ! 
 deactivate-cluster            
 character          
optional  ! 
 apply-constant-el-Fermi-level
  double              
optional  ! 
 apply-constant-hl-Fermi-level
  double              
optional  ! 
$end_quantum-cluster                                
optional  ! 
!-------------------------------------------------------------! 
  
Syntax
cluster-number     =
1 
an integer number to refer to geometry element 
  
region-numbers     =
1 
region numbers, belonging to cluster 
  
deactivate-cluster =
yes 
                 
 =
no 
Flag to switch off quantum clusters (yes|Yes|YES). 
Anything else means NO  (default). 
Switching off quantum means classical simulation. 
This is a very convenient way to turn the quantum mechanical calculation off and 
on. 
  
apply-constant-el-Fermi-level = 
0.2  ! [eV] 
apply-constant-hl-Fermi-level = 0.2  ! 
[eV] 
Applies a constant electron and/or hole Fermi level to this 
quantum cluster. 
 
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