validity of heat transfer by molecular dynamics thomas prevenslik qed radiations discovery bay, hong...

Validity of Heat Transfer by Molecular Dynamics

Thomas PrevenslikQED Radiations

Discovery Bay, Hong Kong

Tribochemistry - HAGI 2011 - HAGI, October 26-28, 2011

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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 give meaningless results at the nanoscale. Moreover, both are invalid by Quantum

Mechanics (QM)

And Propose

How to make MD and FE at least consistent with QM

Introduction

2Tribochemistry - HAGI 2011 - HAGI, October 26-28, 2011

Restrictions

MD and FE are restricted by Statistical Mechanics (SM) to atoms having thermal heat capacity


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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 simulations


4

Today, MD is not made for bulk simulations, but rather for the atomistic response of discrete nanostructures

Problem is QM negates atoms in discrete nanostructures from having heat capacity

Problem


Heat Capacity of the Atom

1

kT

hcexp

hc

E

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Nanostructures

kT 0.0258 eV

SM, MD and FE (kT > 0)

QM(kT = 0)


In nanostructures, the atom has no heat capacity by QM

MD and FE simulations of discrete nanostructures with atoms having heat capacity are a priori invalid

QuestionWhat can be done to allow MD heat transfer of discrete

nanostructures to be at least consistent with QM ?

Argument Summary



Conservation of EnergyLack of heat capacity by QM precludes EM energy conservation in

discrete nanostructures by an increase in temperature, but how does conservation proceed?

Conservation ProposalAbsorbed 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

Up-conversion produces high energy QED photons in tribochemistry, but down-

conversion also occurs, e.g., redshift of galaxy photons in dust in the 2011 Nobel

in physics on an expanding Universe

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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.

Propose EM energy is absorbed almost totally in the NP surface.

Since the NP surface corresponds to the TIR wave function of the QED photons, QED photons are spontaneously created upon EM energy

absorption in NPs.

f = c/ = 2nD E = hf

TIR Confinement


For a spherical NP having diameter D, = 2D


QED Heat Transfer

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QED Photons

Phonons

QQED is non-thermal radiation at TIR frequency

Reduced conductivity in thin films explained by scattering of phonons, but slow to photons

QED Radiation

Tribochemistry Source


At Kyoto, QED photons proposed as the source of tribochemistry

Rubbing was shown to produce NPs - not electrons

TIR converts frictional heating of NPs to QED photons

QED photons have high Planck energy ( e.g., 10 nm NPs produce SXRs at 40 eV )

QED Photons are source of Triboplasma, the electrons and charged ions are produced by Einstein’s photoelectric effect

SXRs → UV consistent with Nakayama and Hiratsuka 11

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).


Pretty Picture v QM Correctness?

MD for Discrete kT = 0, But MD assumes kT > 0

Car distorts but does not move

Macroscopic analogy,

Instead, QM forbids any increase in car temperature. Hence, QED radiation is

produced that by Einstein’s photoelectric effect charges the cars that move by

electrostatic interaction with each other.

MD for kT > 0 is valid for PBC because atoms in macroscopic nanofluid

have kT > 0

Thermal Gradients


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 endCharge is produced

Outer CNT moves under charge gradient to cold end.

Classical physics does not

produce charge

Sputtering


Vienna U. Technology, www. 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..

http://www.matcalc.de/nc/us/white-papers/tribology/

Car - Parrinello MD


[1] See http://www.websters-online-dictionary.org/definitions/Car-Parrinello

The Car-Parrinello in computational chemistry [1] is a type of ab initio (first principles) molecular dynamics,

usually employing periodic boundary conditions, planewave basis sets, and DFT.

[2] R. Car and M. Parrinello, “Unified Approach for Molecular Dynamics and Density-Functional Theory,” Phys. Rev. Let., 55, 2471, 1985.

CPMD formulated [2] for PBC Maybe the word usually is inserted to justify the

many MD simulations that ignored QM

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MD heat transfer based on SM assumes atoms have kT energy which is valid only for PBC

Major problem for MD in Tribology and Tribochemistry because rubbing of surfaces cannot be simulated with 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

QM negates SM, thermal conduction, Fourier Theory, and heat current at the nanoscale.

RecommendationEstimate 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



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

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18Redshift without Universe expansion

Based on classical physics, astronomers assume absorbed galaxy photon increases temperature of dust NPs

Redshift in Cosmic Dust


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

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Nobel Mistake

Astronomers Schmidt, Pearlmutter, and Reiss got the 2011 Nobel in Physics for an accelerated expanding Universe

validity of heat transfer by molecular dynamics thomas prevenslik qed radiations discovery bay, hong...

Documents

capacity md

qm slide

heat capacity problem

md simulations

validity of heat transfer

d slide

equivalent heat transfer

restrictions md