Posted: March 9th, 2010 | Author: obm | Filed under: Physics/Theories, TDDFT | Tags: decomposition, response charge, TDDFPT | No Comments »
In the code I calculate the response charge density at a given frequency from
(1)
where
is the ground state KS orbitals and
is the matrix that contains Krylov subspace of q in real space
)
![Q_{m}=\left[q^1,q^2,\dots,q^m \right]](http://www.obm.cc/cgi/mimetex.cgi?Q_{m}=\left[q^1,q^2,\dots,q^m \right])
(m is the number of Lanczos iterations)
For visualisation purposes I calculate
=\left<\vec{r}\right|\rho^{\prime}\left|\vec{r}\right>)
where
are the points that span the simulation box.
In principle I can also use this operator to obtain the overlap of response charge density at a specific frequency to ground state orbitals.

where
contains the contribution of a valance->conduction transition to the response charge density.
from the construction of (1) any two-photon processes is zero, thus the ith element can be calculated as
^i\phi^j\right>.W_m(\omega))
where index ij is the transition index and j runs through the unoccupied states
Ultrasoft Pseudopotentials
I start with the normalized space

and go to cross-term

then I add the response operator to the left of S operator

\left<\phi_v\right|\right)S\left|\phi^v\right>)
since ground state KS orbitals are orthogonal to each other

)
Thus it appears that no addition of S matrix is necessary.
Posted: February 16th, 2010 | Author: obm | Filed under: Project 21: Extreme, TDDFT | Tags: flavonoid | No Comments »

The following spectra is obtained for the dry system without counter-ion
The cell-size has no significant impact on the spectra of the dry system. The M-T correction does not work, since the cell size is not at least twice the molecule size.
Example input file:
&CONTROL
calculation = "scf",
restart_mode="from_scratch",
prefix="flav-14-nowat-nocl-x2",
pseudo_dir = "/u/cm/mbaris/work/arrigo/pseudo/"
outdir="./out"
/
&SYSTEM
ibrav=8,
celldm(1)=37.794538
celldm(2)=1.0
celldm(3)=0.75
nat=53,
ntyp=3,
ecutwfc=25.0,
ecutrho=200.0,
tot_charge=1.0
occupations="smearing",
smearing="gaussian",
degauss=0.006
/
&ELECTRONS
diagonalization = "cg"
electron_maxstep = 50,
tqr=.true.
/
ATOMIC_SPECIES
C 12.011 C.pbe-van_bm.UPF
O 16.00 O.pbe-van_bm.UPF
H 1.001 H.pbe-van_bm.UPF
ATOMIC_POSITIONS (angstrom)
H 16.022422 8.404178 4.026815
H 16.927685 5.434648 2.237667
H 14.746682 3.281691 1.359805
H 10.229997 3.426490 1.603412
H 11.849385 5.171335 0.566569
H 12.384277 3.542142 1.022973
O 10.665086 4.279735 1.982355
O 12.659925 7.182996 4.571237
O 16.462485 6.291544 2.537711
H 15.173886 5.567365 4.038213
H 14.870297 7.913472 2.112808
O 15.071861 8.237275 4.170719
H 12.596159 8.423016 2.813131
H 12.796823 4.959934 3.511343
C 11.928708 4.470731 1.405801
O 14.875801 3.751071 2.205858
H 14.410707 5.360034 0.955741
C 15.187645 6.001185 2.989469
C 14.553003 7.461131 3.121187
C 13.008388 7.475260 3.162092
O 12.571817 6.611538 2.187258
C 12.876253 5.208181 2.444845
C 14.354138 5.030383 2.071934
H 8.221876 3.334249 5.640921
H 9.458457 13.276892 5.709185
H 4.658234 6.122102 6.725152
H 14.055153 13.956144 4.956817
H 10.915334 5.178283 4.960759
H 6.806275 8.872129 5.448724
H 6.445641 4.601972 6.539093
H 9.439671 10.941687 5.060393
H 14.344719 11.546695 4.865238
H 13.538306 9.221439 5.004162
O 9.383525 8.744544 5.025901
O 8.894354 4.064138 5.738343
O 10.332657 13.506396 5.370300
O 5.096403 7.003869 6.303451
O 12.960550 13.824802 5.203096
C 10.738854 8.618018 4.931856
C 8.577166 7.648407 5.406602
C 11.321160 7.294758 4.831180
C 8.318398 5.251129 5.780359
C 11.073399 12.356283 5.173758
C 9.179369 6.372297 5.447613
C 6.398120 6.752775 6.016743
C 12.493869 12.540966 5.143188
C 11.373125 9.907093 4.943921
C 10.496861 6.146920 5.064049
C 7.222102 7.841186 5.575991
C 6.927668 5.447613 6.087758
C 10.569993 11.097001 5.025261
C 13.265356 11.384291 5.019503
C 12.818361 10.091406 4.991848
K_POINTS {gamma}
Posted: January 19th, 2010 | Author: obm | Filed under: Seminar Notes | Tags: Casimir | No Comments »
Today, Robert J. Jaffe gave a very inspiring talk on Casimir effect. He started from the classical grounded planes and ended up describing a method for calculating more general shapes. Some highlights from his talks are:
- Divergences removed using renormalization theory lead to unphysical results, as there are no terms in the expansion that can cancel the divergence.
- Divergences often result from unphysical conditions imposed on the system, like unphysical boundary conditions. For example assuming a metal to be rigid at every frequency is unphysical.
- The transition from VdW to Casimir forces is continuous, and can be approximated by adding retardation effects to Quantum-Relativistic calculation of VdW.
- Using T matrices and dynamical polarizability of the system, just like how engineers use them to identify material based on their radar signature, Casimir forces can be calculated.
- Dark energy/Casimir correlation is overstated, S matrix theories show casimir effects even without vacuum.
- Many different methods of calculating casimir forces each lead to interesting physics
- Experimental manifestations?
T. Emigetal et Al. PRL 99 170403 (2007) might be interesting to read.