Posted on 11/05/2021 11:14:52 PM PDT by Kevmo
for the cold fusion ping list
https://www.osti.gov/pages/servlets/purl/1433665
Hydrogen adatom interaction on graphene: a first principles
study
Wei Zhang,1,2 Wen-Cai Lu,1,3 Hong-Xing Zhang1
, K. M. Ho2
, and C. Z.
Wang2,*
1
International Joint Research Laboratory of Nano-Micro Architecture Chemistry and
Institute of Theoretical Chemistry, Jilin University, Changchun, Jilin 130023,
People’s Republic of China
2
Ames Laboratory-U.S. DOE and Department of Physics and Astronomy, Iowa State
University, Ames, Iowa 50011, USA
3
Department of Physics and State Key Laboratory Cultivation Base of Advanced
Fibers and Textile Materials, Qingdao University, Qingdao, Shandong 266071,
People’s Republic of China
ABSTRACT
Interaction between two hydrogen adatoms on graphene was studied by
first-principles calculations. We showed that there is an attraction between two H
adatoms on graphene.
However, the strength of interaction between two hydrogen
adatoms and magnetic properties of graphene are strongly dependent on the residence
of the two adatoms on the graphene sublattices. Hydrogen adatoms introduce lattice
distortion and electron localization in graphene which mediate the attractive
interaction between the two H adatoms.
Keywords: Hydrogen adsorption on Graphene; Adatom interaction energy; Lattice
distortion; Electron localization; Magnetic moment
1. Introduction
Graphene is a material of only one atomic layer thick so it is completely exposed to its
environment. Therefore many atoms and molecules can easily adsorb to its surface
and alter the physical properties by disturbing single planar sheet of sp2
-bonded
carbon atoms. For example, graphene can be transformed from a semimetal into a
semiconductor, with a band gap width that can be tuned by controlling the level of
functionalization. There are several different adsorbates that can be used to
functionalize graphene such as gas molecules and radicals [1-3]. A variety of elements
are known to absorb to graphene, such as N, O, H, Fe and Si. Among them, hydrogen
has been the most elusive to study due to its small atomic mass.
Recently, hydrogen adsorption on graphene has attracted enormous attention due
to its unique properties that imply great potential in various kinds of applications [4,
5]. The interaction of atomic hydrogen with graphene is of fundamental interest. A
hydrogen atom is expected to saturate a single carbon pz orbital, forming a local sp3
atomic arrangement, which should significantly alter the local electronic structure due
to the breaking of symmetry within the 2-atom honeycomb unit cell of graphene [6].
The hydrogen-induced changes include a transition from sp2 to sp3 hybridization
which makes graphene-like electronic structure more “diamond-like” at the hydrogen
absorption site but the electronic structures away from the absorption sites are very
close to electronic structure of pure graphene [7]. At high coverage, a band-insulating
behavior has been predicted [8] and possibly observed [2]. On the other hand, low
coverage H or other point defects in graphene are predicted to lead to either
magnetism [9, 10] or a localized insulating state [11-14] depending on whether the H
is arranged orderly or not. Boukhvalov et al. showed the most stable configuration of
low hydrogenated graphene layer corresponds to the non-magnetic pair hydrogen
atoms attached to the different A-B sublattices of graphene [7].
Understanding the basic mechanisms of hydrogen adsorption, interaction,
diffusion and desorption on graphite surfaces is important to understand and solve a
number of scientific and technological problems in fields as diverse as astrophysics
[15, 16], fusion reactor design, and hydrogen storage [17]. In the past decade, H atom
adsorption properties induced structural, electronic, magnetic and chemical
modifications at the graphene sheet have been extensively investigated by various
experiments and theoretical calculations [7, 18-29]. In this paper, using first principles
calculations, we investigate the interaction between two hydrogen adatoms on the
same sublattice and different sublattice of graphene. We show that interaction between
two hydrogen adatoms on graphene is attractive. However, we found that interaction
between two H adatoms on different sublattice of graphene is much stronger than that
on the same sublattice of graphene. The origin of the interactions is also analyzed. We
show that hydrogen adatoms introduce lattice distortion and electron localization in
graphene which mediate the attractive interaction between the two H adatoms.
Results and Discussions
3.1. Interaction energy between hydrogen adatoms
The interaction energy between the two H adatoms on graphene is defined as:
Eint = Ea2 − 2Ea1 (1)
Here, Ea2 is the adsorption energy of two H adatoms simultaneously on graphene, and
Ea1 is the adsorption energy of a single H adatom. Ea2 and Ea1 are the absorption
energy of a pair of hydrogen atoms and a single hydrogen atom respectively defined
by
Ea2 = E2H+gra – (Egra+2μH) and Ea1 = EH+gra – (Egra+μH) with E2H+gra, EH+gra, Egra,
and μH being the total energies of two H-adsorbed graphene, one H-adsorbed
graphene, pure graphene and the chemical potential of a H atom respectively.
The
chemical potential can be chosen as either ½ of the energy of molecular hydrogen or
the energy of hydrogen atom, which will not affect the interaction energy between the
two hydrogen atoms defined in Eq. (1).
To minimize the k-point sampling error in the adsorption energy calculations, the
energies of the isolated perfect graphene sheet and the isolated atom are also
calculated using the same supercell, energy cutoff, and k-point sampling as those in
the calculations for the adatom/graphene systems.
The interaction energy as a function of the distance (Å) between the two
absorbed atoms is shown in Fig. 2. Only the interaction energies between two
hydrogen atoms with the separation distance larger than 4.0 Å are shown in Fig. 2
because we would like to focus more the interaction that is mediated by the graphene
rather than direct bonding between the two hydrogen atoms. We found that the
attraction between two H atoms on different sublattices (AB) is much stronger than
that of on the same sublattices (AA). There is no repulsion between the two H atoms
whether they site on the same sublattices or on different sublattices, as long as the
distance is larger than 4 Å. We note that the calculation based on a theoretical model
by Shytov et al. showed the interaction is attractive for two H on AB sublattices but
repulsive for two H on the same sublattice [41]. The former is consistent with our
calculation but the latter is not. While our calculations are based first-principles
Fig. 2 The distance dependence of the interaction energy for two H adatoms occupied
the different adsorption positions AA and AB along zigzag direction (AA-zz) and
armchair direction (AA-ac and AB-ac).
density function theory where most of the important interactions are considered, not
every interaction term is included in the model of Ref. 41. For example, the effect of
graphene lattice distortion is not explicitly included in the model calculation while
this effect is important as will be discussed in more details below. We also note that
the trend of the interaction energy of our calculation is consistent with the results of
Boukhvalov et al. [7]. Another interesting feature shown in Fig. 2 is that the
interaction between the two H adatoms are very long-range, extended well beyond 14
Å. Obviously such a long-range interaction must be mediated by the underlying
graphene such as elastic distortions and electronic structure modulations discussed
below.
3.2. Lattice distortion in graphene induced by two H atoms adsorption
Adatoms on graphene can induce significant distortions to the graphene lattice. Such
distortions can spread a certain distance from H atom because most of the distortions
Fig. 3. Bond length distortion with respect to that of perfect graphene (1.42 Å) induced by the two
H atoms reside on different sublattices and different distances. The magnitude and the sign of the
distortions are indicated by colors as shown in the bottom of the figure.
are elastic in nature. It is very useful to study the structure distortion caused by
adatoms on graphene. In Fig. 3, we show bond length variation with respect to that of
perfect graphene (1.42 Å) induced by the two H adatoms reside on different position
along ZZ or AC direction. The bonds are found to be compressed in some directions
(cyan) and stretched in other directions (light green). When the distance between two
H atoms is less than 10 Å, large lattice distortions can be well seen at the vicinity of
the two H atoms, some bonds are stretched (red) and some are compressed (blue)
which can also be seen clearly in Fig. 3. Away from the adatoms or the distance of the
two H atoms is about 13 Å, the distortions become negligible in the scale of the plot.
Fig. 4. Bond length distortion and bond-angle distortions with respect to that of perfect graphene
induced by the two H atoms reside on different distance (Å) along AC and ZZ direction.
Conclusion
In summary, the adsorption of two H adatoms on graphene is studied by the
first-principles density-functional calculations. The interaction energies between the
two H adatoms, the lattice distortion on graphene, the interaction electron density and
magnetic properties of hydrogen adsorption are studied. We found that there is a
stronger attractive interaction between two H atoms residing on different sublattices
(AB) than on same sublattices (AA). We further explored the origin of attraction
betwwen the two H adatoms on graphene. We showed two H atoms in graphene
induce substantial lattice distortion to graphene which cost about 2 eV of elastic
energy for the supercell with 200 carbon atoms (or ~10 meV/atom). Through the
study of bond length and bond-angle variation, we found the distortion of AB is larger
than that of AA. We demonstrated the attractive interactions between the two H
adatoms are electronic interaction mediated through graphene due to the graphene
lattice distortion. We also showed that two H atoms residing on the same sublattices
(AA) on graphene introduce magnetic moments while there is no magnetic moment
when two H atoms are sited on different sublattices (AB).
May I have executive summary please? And why should I read this?
Who demanded that you read it? Just click on by if you can’t spare the five minutes that it takes to read it.
Who demanded that you read it? Just click on by if you can’t spare the five minutes that it takes to read it.
It IS an executive summary.
Even the Wikipedia page for “adatom” shows that Graphene acts as a “counterexample” — it is a thermodynamically stable state. Also, since hydrogen is adsorbed into graphene it could provide a lattice structure suitable for controlling the Coulomb Barrier and the resultant heat generation from fusion events.
Adatom
From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Adatom
Adatom according to the TLK model.
An adatom is an atom that lies on a crystal surface, and can be thought of as the opposite of a surface vacancy. This term is used in surface chemistry and epitaxy, when describing single atoms lying on surfaces and surface roughness. The word is a portmanteau of “adsorbed atom”. A single atom, a cluster of atoms, or a molecule or cluster of molecules may all be referred to by the general term “adparticle”. This is often a thermodynamically unfavorable state. However, cases such as graphene may provide counter-examples.[1]
Respectfully, butt out.
Oh OK, thanks, it has to do with cold fusion. That’s a gnarly problem and apparently we don’t have the tools to do it except in the laboratory. And I don’t see how we ever will... As I understand, it requires a sun.
It’s happening in labs across the world. The effect has been replicated more than 150 times in peer reviewed journals.
https://freerepublic.com/focus/f-chat/3963819/posts
No other controversial experiment even comes close to that number of peer reviewed replications. Dolly the Sheep was replicated ONCE.
The Cold Fusion/LENR Ping List
http://www.freerepublic.com/tag/coldfusion/index?tab=articles
Keywords: ColdFusion; LENR; lanr; CMNS
chat—science
—
Vortex-L
http://tinyurl.com/pxtqx3y
Best book to get started on this subject:
EXCESS HEAT
Why Cold Fusion Research Prevailed by Charles Beaudette
https://www.abebooks.com/9780967854809/Excess-Heat-Why-Cold-Fusion-0967854806/plp
Updated No Internal Trolling Rules for FR per Jim Robinson
https://freerepublic.com/focus/f-news/3928396/posts
If someone says stop, then stop. Do not enter onto a thread on a topic you don’t like just to disrupt, rattle cages, poke sticks, insult the regulars, or engage in trolling activities, etc. ~Jim Robinson
Please refrain from posting anything that doesn’t legitimately address the issue.
Something is going on in this segment of science. There are a considerable number of research groups studying the matter. -Sidebar Moderator
Much of the theoretical work that's been done to explain why low-temperature nuclear fusion between hydrogen atoms and between deuterium atoms involves looking at ways hydrogen atoms behave when they're held in close proximity. These experimental results appear to show some attractive behavior between hydrogen atoms when they are adsorbed into a two-dimensional crystal of carbon atoms, a material known as "graphene."
Thus, this could be experimental confirmation of some of the theory that has been developed to explain cold fusion (also sometimes called "LENR").
“...to explain cold fusion (also sometimes called “LENR”).”
Absolutely the first thing I’ve understood in these threads. Thanks.
Julian Schwinger (Physics Nobel Laureate-unfortunately now deceased) did not agree. Neither does a mountain of experimental evidence. Atoms sequestered in a lattice behave differently than atoms in a hot plasma.
What we lack is "engineering reproducibility" to make it happen every time tried.
Is that attractive force what drives H1gas to become H2gas? And by adsorbing into a lattice, does the hydrogen gas in this experiment USE that force to hook up with the lattice atoms? That would point to a separate attractive force.
Something like that, yes. Peter Hegelstein thinks it has something to do with phonon interactions within the lattice. He operates at a level of insight beyond what I have, but I am aware of the concepts and it sounds reasonable to me.
There is no question that nuclear reactions have been observed, on the basis of elemental transmutation, neutron generation, and tritium generation. The only questions are (a) how to understand what's going on, and (b) how to scale up what's going on.
If they can do the theory, there will be a pathway between the nuclear world and the chemical world, which had long been thought to be separated by an enormous energy difference. Such a pathway will have very far-reaching consequences. LENR will only be the beginning.
If they can do the theory, there will be a pathway between the nuclear world and the chemical world, which had long been thought to be separated by an enormous energy difference.
***Here is a video that hints at a place to start:
https://www.youtube.com/watch?v=2UHS883_P60
That built-up chemical energy can take place when hydrogen atoms are compressed together into a lattice, restricting their movement so that their kinetic collisions amplify past the Coulomb barrier.
An in-between state of matter is where all those colliding hydrogen atoms interact with the lattice and end up acting like ONE atom together, a state called Bose-Einstein Condensate, where the Coulomb barrier is known to fall by orders of magnitude.
I combined these two concepts into my Vibrating 1 Dimensional Luttinger Liquid BEC theory, the V1DLLBEC.
https://freerepublic.com/focus/f-chat/3118117/posts?page=3#3
www.mail-archive.com/vortex-l@eskimo.com/msg89493.html
https://www.lenr-forum.com/forum/thread/5859-1-dimensional-lenr-theories/
cool Superwave animation
http://www.youtube.com/watch?v=SoiteXBb1mA&feature=player_embedded
About 3:40 into the animation. I found it at Superwaves’s site
Also:
The interaction that makes H1 gas attract to another H1 atom to form H2 gas is an ENDOthermic reaction. It strongly cools down the surrounding lattice structure. That’s why I think there could be a localized, 1-dimensional temporary BEC formed in that tiny zone.
Focardi said that Rossi’s contribution was disassociating H2 gas into H1 gas when he loaded up the nickel lattice.
In addition, Laser COOLING can generate an internal, localized BEC.
https://www.mail-archive.com/vortex-
Note that they used lasers to REMOVE energy from the system (to COOL it).
That’s what KP Sinha did, and also, what Ed Storms was unaware of here on
Vortex-L until I pointed it out.
https://www.mail-archive.com/vortex-
http://www.internetchemie.info/news/2010/jul10/pinning-transition.html
Pinning Transition from a Luttinger-liquid to an insulated phase
Mott-insulator
*Pinning atoms into order: In an international first, physicists of the
University of Innsbruck, Austria have experimentally observed a quantum
phenomenon, where an arbitrarily weak perturbation causes atoms to build an
organized structure from an initially unorganized one. The scientific team
headed by Hanns-Christoph Nägerl has published a paper about quantum phase
transitions in a one dimensional quantum lattice in the scientific journal
Nature.*
With a Bose-Einstein condensate of cesium atoms, scientists at the
Institute for Experimental Physics of the University of Innsbruck have
created one dimensional structures in an optical lattice of laser light. In
these quantum lattices or wires the single atoms are aligned next to each
other with laser light preventing them from breaking ranks
More information about Hydrogen on Graphene in the same conference.
Abstract:
http://ikkem.com/iccf23/orppt/ICCF23-IA-09-Hu.pdf
Video:
http://ikkem.com/iccf23/MP4/1C-IN09.mp4
Hydrogen isotope separation through two-dimensional crystals
Sheng Hu
College of Chemistry and Chemical Engineering, Pen-Tung Sah Institute of Micro-Nano
Science and Technology, Xiamen University, Xiamen, 361005, China
E-mail: sheng.hu@xmu.edu.cn
Graphene and other two-dimensional (2D) crystals have recently been reported to be able to sieve
hydrogen isotopes with both high hydrogen-to-deuterium selectivity and low energy consumption, at
room temperature. This facilitates the potential developments of 2D materials-based isotope
separation techniques.
This talk will focus on the essential mechanisms for proton transport through
2D crystals, e.g. graphene and hBN, with unexpectedly high transport rates [1]. Then, discuss the
origins of the isotope effects, the proton and deuteron separation factor and the performance and
scalability of the prototype devices [2, 3].
Hydrogen isotopes transport with room temperature
quantum sieving properties through atomic scale channels made of van der Waals crystals will be
discussed as well [4].
References
[1] S. Hu et al., Nature 516, 227-230 (2014).
[2] M. Lozada-Hidalgo†, S. Hu† et al., Science 351, 68-70 (2015).
[3] M. Lozada-Hidalgo; S. Zhang; S. Hu et al., Nat Commun 8, 15215 (2017).
[4] S. Hu et al., Nature Nanotechnol. 13, 468-472 (2018).
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.