Thoughts for us
Penetrating so many secrets, we cease to believe in the unknowable
But there it sits nevertheless, licking its chops.
H. L. Mencken
Heat Transfer in Nanoelectronics
MicroTherm 2013 allows people involved in solving thermal problems in electronics to meet and to present their ideas and achievements in the field of thermal management. The scope of the Conference covers the subjects connected with extreme temperature, electronics, sensors and measurement techniques, modelling, simulation, wide band-gap materials, packaging and reliability, renewable energy sources and photonics with special emphasis on microelectronic technologies.
In microelectronics, heat transfer in circuit elements having dimenisons greater than 1 micron proceeds by classical physics that allows the atom to have heat capcity to conserve Joule heat by an increase in temperature, the analysis of which uses commercial finite element programs such as ANSYS and COMSOL. However, nanoelectronics having dimensions less than 1 micron differs in that QM precludes the atom form having the heat capacity to conserve Joule heat by an increase in temperature. Instead, conservation proceeds by the QED induced conversion of Joule heat to excitons (hole and electron pairs) that charge the circuit element or upon recombiantion emit EM radiation to the surroundings. QM stands for quantum mechanics, QED for quantum electrodynamics, and EM for electromagnetic. Paradoxically, classical physics by allowing the atom to have heat capacity to conserve Joule heat by an increase temperature does not create the charge necessary to change the resistance of the circuit element. See Paper and Presentation
The 2013 Nobel was awarded to Martin Karplus, Michael Levitt and Arieh Warshel for their development of simplified MD methods to simulate the behavior of molecules at various scales, from small molecules to the large proteins in drug design. However, the 2013 Nobel actually recognizes the field of computational chemistry itself rather than particular individuals and certainly was not awarded for the discovery that simplified MD reduces computational resources. In retrospect, the Nobel committee could have selected more prominent MD computational scientists like William Goddard and Michele Parrinello, but did not. In effect, the 2013 Chemistry Nobel was implicitly awarded to every computational scientist who simplifies MD.
Laureates Karplus, Levitt, and Warshel combined QM with classical statistical mechanics to simulate molecular motion using simplified force-field models for various energy dependencies as shown in the thumbnail. But this is not unusual as the MD community knows full well simplified methods are always required to limit computational costs. However, the simplified MD approach still requires experimental data and supporting QM calculations, and may need to be repeated many times perhaps taking as much overall time as the full QM solution.
The 2013 Nobel directed to simplifying MD in the field of computational chemistry by a combination of classical physics and QM although valid for the continuum does not address the validity of the MD solutions for discrete molecules or nanostructures. Unlike classical physics implicit in MD, the problem is QM requires the heat capacity of the atoms in discrete molecules or nanostructures to vanish, and therefore the thermal kT energy of the atoms cannot be related to their momenta. Here k stands for Boltzmann's constant and T for absolute temperature. Alternatively, if the simplified MD simulation is made according to the 2013 Nobel award, the MD solution is still invalid by QM.
The 2013 Nobel committee is to be congratulated for awarding the prize in Chemistry to the collective efforts of the computational chemistry and physics community for simplifying MD computations, but does not go far enough. Simplified MD models alone do not produce valid MD solutions unless QED radiation created by QM is included in the simulations. In this regard, the Nobel falls short of reconciling the invalidity of the uncountable number of discrete MD simulations in the literature, but more importantly fails to provide the guidance going forward to obtain valid MD solutions. See Press Release
The Fourier law implicitly assumes transient thermal disturbances are carried throughout the solid at an infinite velocity while avoiding the mechanism that carries the heat. Paradoxically, phonons and electrons on which the Fourier law is based are limited to acoustic velocities. The paradox is resolved by thermal BB radiation photons finding basis in the harmonic oscillator of Planck’s theory of QM. BB stands for blackbody and QM for quantum mechanics. Instead of carrying the heat of the disturbance, the BB photons created by the atoms carry the temperature of the disturbance throughout the solid at the speed of light, and therefore provide a reasonable approximation to the Fourier law that assumes an infinite carrier velocity, thereby allowing the temperature of atoms at the disturbance as well as the temperature of all other atoms to be instantaneously known everywhere in the solid. The Fourier solution of the transient response of the semi-infinite solid is shown to be virtually identical to that which includes the lag time caused by the speed of light. By QM, thermal BB photons not only explain the success of the Fourier law in describing thermal conduction at the macroscale, but also its failure to do the same at the nanoscale. See Paper and Presentation
Near-field Radiation by Quantum Mechanics
The Planck theory of blackbody radiation giving the dispersion of photons with temperature has served well in the radiative heat transfer between surfaces at the macroscale. Recently, near-field heat transfer by evanescent waves in nanoscale gaps based on solutions of Maxwell’s equation is claimed to exceed by 3-4 orders of magnitude the heat transfer given by Planck theory. However, the Maxwell solutions are questionable because QM precludes the atoms in the surfaces adjacent the gap surfaces under EM confinement `from having the heat capacity to allow the temperature fluctuations necessary to satisfy the FDT. QM stands for quantum mechanics, EM for electromagnetic, and FDT for fluctuation dissipation theorem. Analysis is presented that shows bulk temperatures far removed from the gap do not exist at the gap surfaces, and in fact the temperature differences across gap surfaces tend to vanish. Hence, the Maxwell solutions that assume bulk temperatures abruptly change across gap surfaces over-predict the enhancement of near-field heat transfer by evanescent waves. Instead of evanescent waves, heat is transferred across the gaps between bodies by QED induced tunneling of EM radiation thereby allowing Planck theory to remain valid without modification for nanoscale gaps. QED stands for quantum electrodynamics.
Claims near-field heat transfer is experimentally verified may be safely dismissed because of the abrupt change in bulk temperatures assumed across the gap surfaces in interpreting the data. Similarly, Maxwell solutions that assume heat is transferred across gaps with surfaces coexisting at distinct and different bulk temperatures are consistent with classical physics, but not QM. Indeed, QM refutes the counter-intuitive conjecture that the heat transfer between bodies is actually highest at zero surface spacing. QM aside, it is unphysical to bring bodies to zero spacing without making thermal contact, and therefore it is unlikely any practical device utilizing nanoscale gaps can ever be fabricated to take advantage of the 3-4 orders of magnitude enhancement predicted by Maxwell’s equation for near-field heat transfer by evanescent waves. See Paper and Presentation
past decade, the observation of significant stiffening of nanowires
or NW’s has been reported, although some findings suggest there is
no stiffening. Because of this uncertainty, research on the
mechanism for NW stiffening has been a subject of great interest.
Mechanisms that depend on high surface-to-volume ratio of NW’s
including surface stress and strain have been proposed to explain
stiffening, but cannot explain observations, e.g., NW’s in tensile
tests increase rather than decrease in diameter as expected by
the Poisson effect in classical elasticity theory. Like other
observations at the nanoscale, NW behavior in tensile testing cannot
be interpreted by classical physics.
QM differs by precluding the atoms in NW’s from having the heat capacity to conserve the absorption of EM energy by an increase in temperature. QM stands for quantum mechanics and EM for electromagnetic. In tensile tests, the temperature of the grips that hold the NW during the tensile test do not increase the NW temperature. Instead, the absorbed thermal energy is conserved by frequency up-conversion to the TIR confinement frequency of the NW by QED. TIR stands for total internal reflection and QED for quantum electrodynamics. Under TIR confinement, QED converts the thermal energy into excitons (holon and electron pairs) by the photoelectric effect, the consequence of which is the atoms are charged producing a state of hydrostatic repulsion within the NW. Molecular dynamics simulations that exclude temperature changes consistent with QM show the stiffening of NW’s is caused by the QED induced charge repulsion between atoms. In this way, the usual uniaxial stress state is changed to triaxial having a Poisson effect that increases the wire diameter under tension and enhances the Young’s modulus of the NW. Extensions show QED induced charge repulsion explains the NW stiffening observed if the NW absorbs any form of EM energy - electron beam irradiation or from the Joule heat produced by passing current through NWs.
See Paper and Presentation
The 4th International Conference on Ultrafine Grained and Nano-Structured Materials (UFGNSM) is to be held in Tehran, Iran on 5-6 November 2013. Setting politics aside, the scientific topic selected for discussion is the validity of MD in heat transfer of UFGNSM. MD stands for molecular dynamics.
In computational physics, MD is thought to provide a valid method to derive the atomistic heat transfer response of UFGNSM. MD finds basis in statistical mechanics that assumes atoms always have heat capacity. In the continuum, atoms do indeed have heat capacity, and therefore MD simulations of the continuum made by imposing periodic boundary conditions on an ensemble of atoms are therefore unequivocally valid.
Unlike the continuum, nanostructures comprise discrete ensembles of atoms that lack the periodicity necessary to allow the atom to have the heat capacity required by statistical mechanics. Instead, the heat capacity of the atom is given by QM depending on its EM confinement. QM stands for quantum mechanics and EM for electromagnetic. Nanostructures have high surface to volume ratios, and therefore absorbed EM energy is almost totally absorbed in their surfaces by TIR. TIR stands for total internal reflection. TIR provides EM confinement at short wavelengths shorter than optical frequencies, and therefore by QM the heat capacity of the atom vanishes. Lacking heat capacity, QED induces the absorbed EM energy to be conserved by up-conversion to EM radiation at the TIR frequency of the nanostructure. QED stands for quantum electrodynamics. The QED induced radiation creates excitons that charge the nanostructure or upon recombination are lost to the surroundings. EM confinement by TIR is not permanent, sustaining itself only during the absorption of EM energy. Absent EM energy absorption there is no TIR confinement and QED induced radiation is not created.
MD simulations of nanostructures based on statistical mechanics are therefore invalid by QM. Valid MD simulations require modifications of standard MD programs consistent with the QM requirement that the heat capacity of the atom vanishes. However, the nanotechnology community has been reluctant to accept the necessary MD modifications to obtain valid QM simulations, perhaps because ofthe mistake in unknowingly publishing the invalid MD simulations that abound the literature. Nanotechnology deserves a solid analytical foundation. In this regard, academia by promoting MD theory based on statistical mechanics needs to reconsider QM. Perhaps, QM modifications of MD will begin to be initiated in the newly reformist Iran. See Paper and Presentation
Cancer therapy without the side effect of DNA damage to normal tissue remains perhaps the greatest challenge to medicine. In PDT, NPs with or without non-specific photosensitizers are claimed to destroy cancer tumors upon irradiation with IR lasers. PDT stands for photodynamic therapy, NPs for nanoparticles, and IR for infrared. However, the side effect of PDT is DNA damage as the photosensitizer also binds to adjacent normal tissue cells.
Recently, PIT is claimed to avoid the side effects of DNA damage in PDT by selective destruction of cancer tumors. PIT stands for photoimmunotherapy. PIT differs from PDT by using MAb molecules instead of NPs. MAb stands for monoclonal antibody. MAb molecules bind to specific proteins on the cancer cell membrane. Upon activation by IR light, PIT is claimed to only destroy cancer cells having MAb bound to their cell surface. The PIT mechanism given for tumor necrosis is described by the rapid expansion of local water upon the formation of holes in the cancer cell membrane. However, the rapid expansion of water most certainly cannot proceed without DNA damage of adjacent normal tissue. DNA damage in PIT is not reported, but like PDT the cancer cells are not destroyed without DNA damage.
In normal tissue, DNA damage may occur by alkylating agents and ionizing EM radiation. But alkyl reactions also emit EM radiation, thereby allowing the hypothesis that genotoxicity may be reduced by agents that absorb ionizing UV radiation from the cancer itself. The hypothesis is supported by the fact chemotherapeutic drugs that destroy cancer tumors are also UV absorbers. However, the UV absorption spectrum of DNA is broadband, and therefore it is unlikely the DNA can never be not damaged by any combination of chemo-drugs. DNA damage to normal tissue must therefore occur evidenced by the recurrence of cancer after chemotherapy.
In this arrangement, NPT is proposed to protect the DNA by absorbing all UV radiation independent of its frequency spectrum. NPT stands for nanoparticle therapy. Unlike PDT that uses < 100 nm NPs to destroy cancer tumors, NPT does not destroy tumors, but rather absorbs all UV radiation by using > 300 nm NPs. NPT protects against DNA damage by QED inducing the red-shift of UV radiation irrespective of frequency to non-damaging IR radiation. QED stands for quantum electrodynamics. In this regard, NPs > 300 nm are therefore perfect UV absorbers. See Paper .
Measuring the thermal properties of nanoscale samples at any
temperature, let alone temperatures of 4000 K is, to say the least, quite
controversial. Nevertheless, claims have been made that a thermal test
platform is capable of operating at extreme temperatures as high as 4000 K
while allowing local temperatures to be inferred with nanoscale resolution.
The thermal test platform comprises a suspended Si3N4 membrane on which are placed gold NPs that act as thermometers noted above as nano crystals. NP stands for nanoparticle. Current is shown passing through the membrane provides the Joule heat that is thought to create the extreme temperatures. Gold NPs <10 nm are thought to allow local temperatures to be inferred because they evaporate immediately upon melting, e.g., 6 nm NPs are considered to melt at 1275 K. In measurements, temperatures at a point on the platform at the instant the evaporating NPs disappear are inferred to be 1275 K.
However, claims the thermal platform allows the extreme temperature response of nanoscale samples to be inferred from the evaporation of gold NPs may be safely dismissed by QM. QM stands for quantum mechanics. Yet, the QM restrictions are not limited to the instant thermal platform based on temperatures for the vaporization of NPs, but rather more generally to the wide spread use of classical physics in nanotechnology.
In classical physics, the heat capacity of the atom is constant at kT from the macroscale to the nanoscale. Here, k is Boltzmann's constant and T absolute temperature. The instant thermal platform that infers temperature from the vaporization of gold NPs is therefore consistent with classical physics, but unfortunately not QM. In fact, QM by the Einstein-Hopf relation for the atoms in the NPs as harmonic oscillators requires the heat capacity to vanish. See Paper "Zero Specific Heat"and Presentation here on page 2010.
At the nanoscale, heat may only be conserved by QED induced EM radiation. QED stands for quantum electrodynamics and EM for electromagnetic. Indeed, absorbed EM energy of any kind in a nanoscale sample cannot be conserved by an increase in temperature because QM requires the atom to have vanishing heat capacity under its own TIR confinement. TIR stands for total internal reflection. Instead, conservation proceeds by the creation of non-thermal EM radiation at the TIR resonant frequency of the nanoscale sample. Lacking heat capacity by QM, QED conserves the Joule heat at the TIR frequency of the NP by creating excitons (holon and electron pairs) that charge the NPs or upon recombination are emitted to the surroundings as QED radiation.
What this means is there are no extreme temperatures that vaporize the NPs. Instead, the NPs vaporize as the QED induced EM radiation ionizes the atoms to produce a Coulomb explosion. See