Solution LAB1 ecutwfc convergence 3 - Revision history

Andrea Ferretti at 12:55, 9 December 2020

2020-12-09T12:55:53Z

← Older revision		Revision as of 12:55, 9 December 2020
Line 1:		Line 1:

	* Back to the previous page: [[Structural and electronic properties of semiconductors and metals #~~Exercises~~]]		* Back to the previous page: [[Structural and electronic properties of semiconductors and metals #Convergences]]

	=== Convergence of the total energy differences and forces wrt the kinetic energy cutoff ===		=== Convergence of the total energy differences and forces wrt the kinetic energy cutoff ===

Andrea Ferretti: /* Convergence of the total energy differences and forces wrt the kinetic energy cutoff */

2020-12-09T11:45:41Z

Convergence of the total energy differences and forces wrt the kinetic energy cutoff

@@ Line 34: / Line 34: @@
 As discussed, by displacing one atom we are breaking the symmetry of the system and atomic forces different from zero can arise. This is indeed the case.
-Here we can first compare the total energy differences (wrt the pristine undistorted case) as a function of kinetic energy cutoff.
+Here we can first compare the '''total energy differences''' (wrt the pristine undistorted case) as a function of kinetic energy cutoff.
 Plot is given in the figure:
 [[File:Data etot diffdispl log.jpg|450px|Total Energy differences vs Kinetic energy cutoff ]]
 Next, we can also plot the behaviour of atomic forces wrt ecutwfc.

Andrea Ferretti: Created page with " * Back to the previous page: Structural and electronic properties of semiconductors and metals #Exercises === Convergence of the total energy differences and forces wrt..."

2020-12-09T11:29:00Z

Created page with " * Back to the previous page: Structural and electronic properties of semiconductors and metals #Exercises === Convergence of the total energy differences and forces wrt..."

New page

* Back to the previous page: [[Structural and electronic properties of semiconductors and metals #Exercises]]

=== Convergence of the total energy differences and forces wrt the kinetic energy cutoff ===

We can use the same script as before, adding a displacement as suggested (0.05 or 0.10 alat to the component of one of the atoms in the cell).

We also want to modify the scheme for file naming (i.e. te label variable).

In practice, we can modify the script according to the following snippets:
#
# set vars
#
nk=8
alat=6.741
displ=0.01
#
ecutwfc_list="20 30 40 50 60 80 100 120 140 160 200 300 400"
[...]

label="nk${nk}_displ${displ}_ecut${ecutwfc}"
[...]

# input file
&CONTROL
[...]
tprnfor=.true.
/
[...]
ATOMIC_POSITIONS (alat)
C 0.00 0.00 0.00
C 0.25 0.25 $((0.25+$displ))

As discussed, by displacing one atom we are breaking the symmetry of the system and atomic forces different from zero can arise. This is indeed the case.

Here we can first compare the total energy differences (wrt the pristine undistorted case) as a function of kinetic energy cutoff.
Plot is given in the figure:

[[File:Data etot diffdispl log.jpg|450px|Total Energy differences vs Kinetic energy cutoff ]]

Next, we can also plot the behaviour of atomic forces wrt ecutwfc.