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

http://en.wikipedia.org/wiki/Particle_in_a_one-dimensional_lattice_(periodic_potential)#Kronig.E2.80.93Penney_model

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

• need a centralized code

• 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

##computing

https://www.nimbisservices.com/page/what-cloud-services-mathematica