1. Unphysical Heat Transfer by Molecular Dynamics Thomas Prevenslik QED Radiations Discovery Bay, Hong Kong Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012 1

2. 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 Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012

3. MD and FE Restrictions MD and FE are restricted by Statistical Mechanics (SM) to atoms having thermal heat capacity Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012 3

4. 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 MD is therefore valid for bulk PBC simulations Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012 4

5. Today, MD is not made for bulk simulations, but rather for the atomistic response of discrete nanostructures Problem is MD programs are based on SM and assume the atom has heat capacity that leads to unphysical results Conductivity in Thin films depends on thickness Nanofluids violate mixing rules Problem 5 Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012

6. Heat Capacity of the Atom 6 Nanostructures kT 0.0258 eV SM, MD and FE (kT > 0) QM (kT = 0) Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012 In nanostructures, the atom has no heat capacity by QM

7. Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 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

8. If the refractive index of nanostructure is greater than that of surroundings, the proposed QED photons are confined by TIR 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 of the QED photons. QED photons are created upon EM energy absorption in NPs. f = c/ = 2nD E = hf TIR Confinement 8 Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012

9. QED Heat Transfer 9 QED Photons Phonons Q QED is non-thermal radiation at TIR frequency Q abs conserved by Q QED photons before thermalization and phonons Charge QED photons create charge or are emitted to surroundings

10. 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, 074302 (2007). 10 Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 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 QM differs No increase in car temperature Charge is produced photoelectric effect Cars move by electrostatic interaction MD for kT > 0 is valid for PBC because atoms in macroscopic nanofluid have kT > 0

11. Thermal Gradients Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012 11 Q-W Hou, B-Y Cao and Z-Y Guo,“Thermal gradient induced actuation of double-walled carbon nanotubes,”, Nanotechnology, Vol. 20, 495503, 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

12. Sputtering Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012 12 Vienna U. Technology, www. Research Group Surface & Plasma Technology -.mhtwww. Research Group Surface & Plasma Technology -.mht MD 5 keV Ar atoms Impacting Cu One answer to question: 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..

13. 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 Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012

14. Questions & Papers Email: nanoqed@gmail.com http://www.nanoqed.org Inter. Conf. Frontiers Mechanical/Materials Engineering (MEME), Hong Kong, July 27-29, 2012 14