Javier Junquera - PowerPoint Presentation

Slide1

Javier Junquera

Exercises on basis set generationControl of the range of the second-ς orbital: the split norm Slide2

Most important reference followed in this lectureSlide3

Default mechanism to generate multiple- in SIESTA:

“Split-valence” method

Starting from the function we want to suplementSlide4

Default mechanism to generate multiple- in SIESTA:

“Split-valence” method

The second-

 function

reproduces the tail of the of the first-

 outside a radius

r

mSlide5

Default mechanism to generate multiple- in SIESTA:

“Split-valence” method

And continuous smoothly towards the origin as

(two parameters: the second-

 and its first derivative continuous at

r

mSlide6

Default mechanism to generate multiple- in SIESTA:

“Split-valence” method

The same Hilbert space can be expanded if we use the difference,

with the advantage that now the second-

 vanishes at r

m

(more efficient)Slide7

Default mechanism to generate multiple- in SIESTA:

“Split-valence” method

Finally, the second- is normalized

r

m

controlled with

PAO.SplitNormSlide8

Meaning of the

PAO.SplitNorm parameterPAO.SplitNorm is the amount of the norm (the full norm tail + parabolla norm

) that the second-

ς

split off orbital has to

carry

(typical value 0.15

)Slide9

Bulk Al, a metal that crystallizes in the fcc

structureGo to the directory with the exercise on the energy-shift

Inspect the input file,

Al.energy-shift.fdf

More information at the Siesta web page

http://www.icmab.es/siesta

and follow the link Documentations, Manual

As starting point, we assume the theoretical lattice constant of bulk Al

FCC lattice

Sampling in k in the first

Brillouin

zone to achieve self-consistencySlide10

For each basis set,

a relaxation of the unit cell is performedVariables to control the Conjugate Gradient minimization

Two constraints in the minimization:

- the position of the atom in the unit cell (fixed at the origin)

- the shear stresses are nullified to fix the angles between the unit cell lattice vectors to 60

°, typical of a fcc latticeSlide11

The splitnorm

: Variables to control the range of the second-ς shells in the basis set Slide12

The splitnorm

: Run Siesta for different values of the PAO.SplitNorm

PAO.SplitNorm 0.10Edit

the

input file and set up

Then

,

run

Siesta

$siesta <

Al.splitnorm.fdf

> Al.splitnorm.0.10.outSlide13

For each splitnorm

, search for the range of the orbitalsEdit each output file and search for:Slide14

Edit each output file and search for:We are interested in

this number

For each splitnorm

, search for the range of the orbitalsSlide15

Edit each output file and search for:The lattice

constant in this particular case would be2.037521 Å × 2 = 4.075042 Å

For each splitnorm, search for the range of the orbitalsSlide16

For each energy shift, search for the timer per SCF step

We are interested in this numberSlide17

The SplitNorm

: Run Siesta for different values of the PAO.SplitNorm

PAO.SplitNorm 0.15 Edit

the

input file and set up

Then

,

run

Siesta

$siesta <

Al.splitnorm.fdf

>

Al.

splitnorm.0.15

.out

Try different values of the

PAO.EnergyShift

PAO.SplitNorm

0.20

$siesta <

Al.splitnorm.fdf

>

Al.

splitnorm.0.20

.out

PAO.SplitNorm

0.25

$siesta <

Al.splitnorm.fdf

>

Al.

splitnorm.0.25

.outPAO.SplitNorm 0.30

$siesta < Al.splitnorm.fdf > Al.splitnorm.0.30.out

PAO.SplitNorm

0.10$siesta < Al.splitnorm.fdf

> Al.splitnorm.0.10.outSlide18

Analyzing the results

Edit in a file (called, for instance, splitnorm.dat) the previous values as a function of the SplitNormSlide19

Analyzing the results: range of the orbitals as a function of the split norm

$ gnuplot$ gnuplot> plot ”splitnorm.dat" u 1:2 w l, ”splitnorm.dat" u 1:3 w l$ gnuplot> set terminal postscript color$ gnuplot> set output “range-2zeta.ps”$

gnuplot> replot

The

larger

the

SplitNorm

,

the

smaller

the

orbitals