vc supergroup
##2-,3-,n-phonon processes
comparison to QFT as a perturbation theory
http://en.wikipedia.org/w/index.php?title=File:Feynman_EP_Annihilation.svg&page=1
http://www.iue.tuwien.ac.at/phd/pourfath/node122.html
typically stop at 3-phonon, minimum required.
##ald with dft
###many-body qm dirac equation http://en.wikipedia.org/wiki/Dirac_equation qm + special relativity -> spin, antimatter
Psi(x) = psi(x1)...psi(xn)
###plane-wave dft
current limiation of plane-wave dft:
( limit O(100 atoms) ) per 1 min (BCS = best case scenario, Si perfect supercell) ald_num_calc_necessary = O(1000) - O(2^20,1000000)
calcultion time = O(1) - O(2^10/60 = 17 hours )
md_num_atoms_necessary = 1000
dft_calc_scaling = dft_calc_scaling(size(icurrent-1))^3
calcultion time_necessary = O( 41 ) - O( 700 days )
linear scaling dft methods: bigdft
###anharmonic ald (small unit cells) <- anharmonic + harmonic (large unit cells) -> harmonic (very large unit cells, amorphous)
run AF using a gaussian distribution of spring cosntants, of varying width. Can u make the thermal conductivt much lower using k_avg = 1?
##discussion
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need a centralized code
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need to scan the database of materials using a combination of techinques
ab-initio FCs + scaling laws + varying size unit cells and supercells ( limit O(100 atoms) )
example:
http://www.pssclabs.com/life-sciences/computational-chemistry/hpc-cluster
$45000 = 108 cores, 255 gb ram
symmetry optimized code
time for phonon properties,thermal conductivity = 1 hr
time for alloy prediction = 1 hr + 10s