Invalidity of Molecular Dynamics in Heat Transfer Thomas Prevenslik QED Radiations Discovery Bay, Hong Kong 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept ,

Molecular Dynamics (MD) is commonly used to simulate heat transfer at the nanoscale in the belief: Atomistic response using L-J potentials (ab initio) is more accurate than macroscopic finite element (FE) programs, e.g., ANSYS, COMSOL, etc. In this talk, I argue: FE gives equivalent heat transfer to MD, but both are invalid at the nanoscale by Quantum Mechanics (QM) And ask the question: How to make MD and FE at least consistent with QM? Introduction 2 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012

MD and FE Restrictions MD and FE are restricted by Statistical Mechanics (SM) to atoms having thermal heat capacity 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept ,

Validity Historically, MD simulations of the bulk performed in submicron computation boxes under periodic boundary conditions (PBC) assume atoms have heat capacity In the macroscopic bulk being simulated, all atoms do indeed have heat capacity (Computation box taken from bulk for analysis) MD is therefore valid for bulk PBC simulations 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept ,

Today, MD is not made for bulk simulations, but rather for the atomistic response of discrete nanostructures Problem is MD programs based on SM assume the atom has heat capacity that I will show is the cause of the unphysical results Conductivity in Thin films depends on thickness Nanofluids violate mixing rules, etc Why is this so? Problem 5 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012

Heat Capacity of the Atom 6 Nanostructures kT eV SM, MD and FE (kT > 0) QM (kT = 0) 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012 In nanostructures, the atom has no heat capacity by QM

2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012 Conservation of Energy Lack of heat capacity by QM precludes EM energy conservation in discrete nanostructures by an increase in temperature, but how does conservation proceed? Proposal Absorbed EM energy is conserved by creating QED photons inside the nanostructure - by frequency up or down - conversion to the TIR resonance of the nanostructure. QED = Quantum Electrodynamics TIR = Total Internal Reflection 7 QED photons create charge or emitted to surroundings

If the refractive index of nanostructure is greater than that of surroundings, the proposed QED photons are confined by TIR ( Tyndall, 1870 ) NPs have high surface to volume ratio. EM energy is absorbed almost totally in the NP surface. The NP surface is the TIR wave function shape of QED photons. QED photons are created upon EM energy absorption. f = c/ = 2nD E = hf TIR Confinement 8 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012

QED Heat Transfer 9 QED Photons Phonons Charge  T = 0

MD - Discrete and PBC Akimov, et al. “Molecular Dynamics of Surface- Moving Thermally Driven Nanocars,” J. Chem. Theory Comput. 4, 652 (2008). Sarkar et al., “Molecular dynamics simulation of effective thermal conductivity and study of enhance thermal transport in nanofluids,” J. Appl. Phys, 102, (2007). 10 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012 Pretty Picture v QM Correctness? MD for Discrete  kT = 0, But MD assumes kT > 0 Car distorts but does not move Macroscopic analogy, FE = MD Classical Physics does not work QM differs No increase in car temperature Charge is produced photoelectric effect Car move by electrostatic interaction MD for kT > 0 is valid for PBC because atoms in macroscopic nanofluid have kT > 0

Thermal Gradients 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , Q-W Hou, B-Y Cao and Z-Y Guo,“Thermal gradient induced actuation of double-walled carbon nanotubes,”, Nanotechnology, Vol. 20, , 2009 MD of Concentric CNTs With MD, no CNT motion found. Motion by adding a thermophoretic spring, but then no need for MD By QM, more QED radiation is produced at hot than cold end Charge is produced Outer CNT moves under charge gradient to cold end. Classical physics does not produce charge

Sputtering 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , Vienna U. Technology, www. Research Group Surface & Plasma Technology -.mhtwww. Research Group Surface & Plasma Technology -.mht MD 5 keV Ar atoms Impacting Cu What can be done? During MD solution, use Nose-Hoover thermostat to hold temperature constant as required by QM. The QED radiation emitted is the net thermostat heat. Input the QED radiation in FE programs to determine effect on the surroundings..

MD heat transfer based on SM assumes atoms have kT energy which is valid only for PBC MD simulations of discrete nanostructures do not produce charge and are meaningless, except for pretty pictures. MD and FE provide equivalent heat transfer simulations of discrete nanostructures, but both are invalid by QM and give unphysical results QM negates SM, thermal conduction, Fourier Theory, and heat current at the nanoscale Recommendation Estimate the time-history of QED radiation and use in FE simulations to determine the effect on macroscopic surroundings. MD may not even be necessary Conclusions 13 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012

Expanding Unverse In 1929, Hubble measured the redshift of galaxy light that by the Doppler Effect showed the Universe is expanding. But cosmic dust of submicron NPs permeate space and redshift galaxy light without Universe expansion 14

2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , Redshift without Universe expansion Based on classical physics, astronomers assume absorbed galaxy photon increases temperature of dust NPs Redshift in Cosmic Dust

2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept , 2012 Referring to his calculation showing acccelerated Universe expansion, Reiss is quoted as saying: "I remember thinking, I've made a terrible mistake and I have to find this mistake" Others said: “[Riess] did a lot after the initial result to show that there was no sneaky effect due to dust absorption“ Reiss did make a mistake - Redshift does occur in dust No Universe expansion, accelerated or otherwise 16 Nobel Mistake Astronomers Schmidt, Pearlmutter, and Reiss received the 2011 Physics Nobel for discovery of an accelerated expanding Universe

Questions & Papers 2nd Inter. Conf. Nanomaterials: Applcations & Properties - NAP, Alushta, Sept ,