EPW Forum

Dear all,

I want to calculate the nesting function for a two dimensional compound.
The coarse k/q-meshes are chosen to be 16x16x1. And the fine k/q-meshes
are 200x200x1.

I set nest_fn=.true. in the input file for epw. But when I check the nesting
function, I found extremely large values. For example, the values of nesting function
at Gamma point for different smearing parameters are as follows.

(I set degaussw=0.005, nsmear=30, and delta_smear=0.01.
Thus we got 30 values for different smearing parameters.)

Nesting function (q)= 0.768762E+04 [Adimensional]
Nesting function (q)= 0.197138E+07 [Adimensional]
Nesting function (q)= 0.504677E+09 [Adimensional]
Nesting function (q)= 0.129197E+12 [Adimensional]
Nesting function (q)= 0.330745E+14 [Adimensional]
Nesting function (q)= 0.846707E+16 [Adimensional]
Nesting function (q)= 0.216757E+19 [Adimensional]
Nesting function (q)= 0.554898E+21 [Adimensional]
Nesting function (q)= 0.142054E+24 [Adimensional]
Nesting function (q)= 0.363658E+26 [Adimensional]
Nesting function (q)= 0.930964E+28 [Adimensional]
Nesting function (q)= 0.238327E+31 [Adimensional]
Nesting function (q)= 0.610117E+33 [Adimensional]
Nesting function (q)= 0.156190E+36 [Adimensional]
Nesting function (q)= 0.399846E+38 [Adimensional]
Nesting function (q)= 0.102361E+41 [Adimensional]
Nesting function (q)= 0.262043E+43 [Adimensional]
Nesting function (q)= 0.670830E+45 [Adimensional]
Nesting function (q)= 0.171733E+48 [Adimensional]
Nesting function (q)= 0.439635E+50 [Adimensional]
Nesting function (q)= 0.112547E+53 [Adimensional]
Nesting function (q)= 0.288119E+55 [Adimensional]
Nesting function (q)= 0.737586E+57 [Adimensional]
Nesting function (q)= 0.188822E+60 [Adimensional]
Nesting function (q)= 0.483384E+62 [Adimensional]
Nesting function (q)= 0.123746E+65 [Adimensional]
Nesting function (q)= 0.316791E+67 [Adimensional]
Nesting function (q)= 0.810984E+69 [Adimensional]
Nesting function (q)= 0.207612E+72 [Adimensional]
Nesting function (q)= 0.531487E+74 [Adimensional]

Is this situation normal? One more question, can we compare the absolute values of nesting function
for different conditions (e.g. between pristine and electron doped cases)?
Thanks in advances. Any help will be highly appreciated!

Best wishes,
Miao Gao
Ningbo University