#Science #Chemistry #MendeleevNumbers #MaterialProperties
Russian scientists crack Mendeleev mystery
Russian scientists have created a chemical space mapping method and cracked the mystery of Mendeleev Numbers.
Scientists had long tried to come up with a system for predicting the properties of materials based on their chemical composition until they set sights on the concept of a chemical space which places materials in a reference frame such that neighboring chemical elements and compounds plotted along its axes have similar properties.
This idea was first proposed in 1984 by the British physicist, David G. Pettifor, who assigned a Mendeleev number (MN) to each element.
Yet the meaning and origin of MNs were unclear. Scientists from the Skolkovo Institute of Science and Technology (Skoltech) puzzled out the physical meaning of the mysterious MNs and suggested calculating them based on the fundamental properties of atoms.
They showed that both MNs and the chemical space built around them were more effective than empirical solutions proposed until then. Their research supported by a grant from the Russian Science Foundation’s (RSF) World-class Lab Research Presidential Program was presented in The Journal of Physical Chemistry C.
Systematizing the enormous variety of chemical compounds, both known and hypothetical, and pinpointing those with a particularly interesting property is a tall order. Measuring the properties of all imaginable compounds in experiment or calculating them theoretically is downright impossible, which suggests that the search should be narrowed down to a smaller space.
David G. Pettifor put forward the idea of a chemical space in the attempt to somehow organize the knowledge about material properties. The chemical space is basically a reference frame where elements are plotted along the axes in a certain sequence such that the neighboring elements, for instance Na and K, have similar properties.
The points within the space represent compounds, so that the neighbors, for example NaCl and KCl, have similar properties, too. In this setting, one area is occupied by superhard materials and another by ultrasoft ones.
Having the chemical space at hand, one could create an algorithm for finding the best material among all possible compounds of all elements. To build their “smart” map, Skoltech scientists, Artem R. Oganov and Zahed Allahyari, came up with their own universal approach that boasts the highest predictive power as compared to the best known methods.
For many years scientists were clueless as to how Pettifor derived his MNs (if not empirically), while their physical meaning remained a nearly “esoteric” mystery for years.
“I had been wondering about what these MNs are for 15 years until I realized that they are most likely rooted in the atom’s fundamental properties, such as radius, electronegativity, polarizability, and valence. While valence is variable for many elements, polarizability is strongly correlated with electronegativity.
This leaves us with radius and electronegativity which can be reduced to one property through a simple mathematical transformation. And here we go: we obtain an MN that turns out to be the best way to describe all the properties of an atom, and by a single number at that,” explains Artem R. Oganov, RSF grant project lead, a professor at Skoltech and MISiS, a Member of the Academia Europaea, a Fellow of the Royal Society of Chemistry (FRSC) and a Fellow of the American Physical Society (APS).
The scientists used the calculated MNs to arrange all the elements in a sequence that posed as the abscissa and ordinate axes at the same time. Each point in space In corresponds to all compounds of the corresponding elements. In this space, using measured or predicted properties of compounds, one can map any specific characteristic, for example, hardness, magnetization, enthalpy of formation, etc. A property map thus produced clearly showed the areas containing the most promising compounds, such as superhard or magnetic materials
The miniature Voyager, 15 micrometers (0.015 millimeters) long, is part of a project researchers at Leiden University conducted to understand how shape affects the movement and interactions of micro-swimmers. Micro-swimmers are small particles that can move independently through liquid by interacting with their surroundings through chemical reactions. The platinum coating on the micro floats reacts to a hydrogen peroxide solution that they are placed in and that propels them through the liquid.#science #StarTrek
I’m reaching out to you with some disheartening news. We had another
cable break at the Arecibo Observatory Friday night. We will be
notifying the broader community later this morning, but I wanted you to
hear it first from us.
A main cable that supports the Arecibo Observatory broke Friday at about
7:40 p.m. Puerto Rico time.
Unlike the auxiliary cable that failed on Aug. 10, this main cable did
not slip out of its socket. It broke and fell onto the reflector dish
below causing additional damage to the dish and other nearby cables. No
one was hurt and engineers are already working to determine the best way
to stabilize the structure.
A safety zone has been set up around the dish out of an abundance of
caution and only personnel needed to respond to the incident are allowed
We haven’t determined why the main cable broke, but we suspect it is
related to the extra load the remaining cables have been carrying since
August. A monitoring team has been closely watching all the cables and
platform since then as part of the facility’s safety and temporary
emergency repair plan. We had noted and were tracking broken wires on
the main cable that failed Friday. As timing would have it, we were
waiting for a team of engineers scheduled to arrive Tuesday, Nov. 10,
who were expected to begin temporary emergency repairs related to the
This is certainly not what we wanted to see, but the important thing is
that no one got hurt. We have been thoughtful in our evaluation and
prioritized safety in planning for the repairs that were supposed to
begin Tuesday. Now this. There is much uncertainty until we can
stabilize the structure. It has our full attention and we are working
with our partners and stakeholders. We are evaluating the situation and
hope to have more to share soon.
We’ve been working with the engineering firms WSP, Thornton Thomasetti
and Wiss, Janney, Elstner Associates Inc. since Friday night to come up
with a strategy to address the new break. You’ll remember we retained
these firms in September in connection with the first cable failure. We
have also been in touch with NSF and they know the situation is urgent.
Our current plan is to reduce the tension in the existing cables at
tower 4 and install steel reinforcements to temporarily alleviate some
of the additional load that is being distributed among the remaining
cables. We are mobilizing to do the work as quickly as possible. We are
also attempting to expedite the arrival of two new cables that were
already on order. That’s the current plan pending further evaluation,
which will be taking place over the next few days.
We also have a supplemental funding request pending NSF approval to make
temporary repairs related for the original break. There is no cost
estimate for the new repairs that will be needed at this time. We will
continue to update you on our progress.
I know 2020 has been a tremendously challenging year. This is a setback.
But we remain committed to getting the facility back online.
The antenna in question is named Deep Space Station 43 (DSS43) and is located just outside Canberra, Australia's capital city. The facility's 70-metre-wide main dish is 48 years old, and the only antenna of that size in the southern hemisphere. As Voyager 2 is heading southwards compared to Earth's orbital plane, only a dish south of the equator can send the probe a sufficiently powerful signal.https://www.theregister.com/2020/11/03/voyager_2_back_online/