After he finished taking notes, Lu Mingyuan looked at Li Dong and asked his second question.
This question was about the probe tip geometry in the LT-STM.
"In your expansion of κ, the part for the probe tip uses a phenomenological approximation based on the work function and the tip’s geometry."
"But for a setup with a PtIr tip, a SiO2 insulating layer, and gold plating for grounding, the tip’s end face has nanoscale irregularities after being milled by a focused ion beam."
"How does your phenomenological approximation account for these irregularities?"
Li Dong’s reply was quick.
"Teacher Lu, the irregularities in the probe tip section affect the height of the effective potential barrier."
"It doesn’t enter the planar geometry term."
"In my formulation, it ultimately just scales the pre-factor of the overall tunneling transmission probability."
"The pre-factor is a global scaling factor."
"It doesn’t affect the three distinct segments of exponential decay that emerge at the tail of the third shell."
Wu Kai was starting to get lost. After all, this wasn’t his area of expertise.
"Old—"
He was about to ask Lu Mingyuan a question when he noticed Lu Mingyuan’s pen flying across the page.
Wu Kai...
Just then, Lu Mingyuan finished his notes. He glanced at Wu Kai, and the look said it all.
It looked like the project was truly about to change direction.
Then he turned back to Li Dong and said bluntly,
"Let’s go."
"Let’s go run it."
Li Dong smiled.
He took a USB drive out of his backpack.
"Teacher Lu."
"I’ve already run it."
Hearing this, both Wu Kai and Lu Mingyuan were taken aback.
"You’ve already run it?"
"What did you run it on?"
"Our group’s SX-STM won’t be available until we get beamline time next month at the earliest."
"That distance-current decay curve in the vacuum section... without that machine, how did you plot it?"
Li Dong shook his head.
"Teacher Lu, I didn’t touch the SX-STM part."
"I didn’t touch the X-ray polarization part either. That will have to wait for you to arrange."
"I ran this part."
He pointed to the paper outlining his three-component model.
"The DFT portion. I ran it on the group’s high-performance server cluster, comparing the real representation of the dipole matrix elements under three different basis sets."
This method of running the simulation couldn’t be considered rigorous experimental data.
It was using a few existing pieces of equipment to "cobble together" a preliminary outline of the most critical data that the yet-to-arrive SX-STM would produce.
To a seasoned experimentalist, this kind of workaround was a known quantity.
It wasn’t a real experiment. It was just a quick validation to "confirm the direction" first.
When Wu Kai himself was young, he had done the same thing when faced with a bottleneck where a proper experiment wasn’t possible.
But you would never teach this sort of thing to a novice.
It was a veteran’s under-the-table trick.
It wasn’t rigorous.
It wasn’t scientific.
If you put it out there, wrote it in a paper, you’d get blasted by the reviewers.
Lu Mingyuan glanced at Wu Kai.
The meaning in his eyes was obvious.
’Did you teach him this?’
Wu Kai shook his head.
He really hadn’t taught him.
Lu Mingyuan looked at Li Dong.
"Where’s the data?"
Li Dong handed him the USB drive.
The three of them sat down in front of the computer in the small office.
Li Dong opened the folders on the USB drive one by one.
The DFT set came up first.
The comparison of the dipole matrix elements under the three basis sets showed a clean phase difference of 0.
Then the XPS set.
The scan of the oxidation state of the iron-centered complex matched the initial DFT value to two decimal places.
Finally, there was the LT-STM set.
On the screen, the distance-current decay curve faintly split into three segments at its tail end.
Li Dong matched those three segments to the κ1, κ2, and κ3 from yesterday’s stack of draft papers.
The exponential slope of each segment perfectly matched the corresponding κ value from his calculations.
Wu Kai and Lu Mingyuan stared at the screen, neither of them speaking.
After a long while,
Wu Kai was the first to let out a sigh.
He turned his head.
"Old Lu."
"What do you think?"
Lu Mingyuan’s voice wasn’t loud.
"Old Wu, if there are no issues with this data..."
"Our approach could put us a huge step ahead of every other project team like this in the world."
"We might even have pushed this project halfway to completion already."
"And then we’ll be stuck on the hardest problem."
Wu Kai knew what "the hardest problem" Old Lu was talking about.
This "X-ray characterization of a single atom" project... what their group truly wanted to achieve wasn’t just lifting an isolated iron atom off a gold surface.
What they wanted to do was to turn this single iron atom from a static "sample" into a living, breathing single-atom nanozyme that scavenges reactive oxygen species during a catalytic reaction.
In situ, real-time.
To read out the element, chemical state, orbital orientation, and coordination environment of an iron atom while it is reacting.
This was the final summit they had to conquer.
It was also the most difficult problem of the entire project.
Li Dong’s approach had bypassed the first two walls they’d been up against.
It had taken the project team from a position of constantly hitting a wall and kicked them straight into the second half of the game.
Next, it was time to climb that highest peak.
"Come on."
"Let’s go get everyone."
「Ten minutes later.」
In the laboratory.
All the members of the project team were gathered together.
Cheng Duo, Lu Heng, Shen Ying, Guo Han, Su Yanqing, Zhang Yan...
Standing before them were Wu Kai, Lu Mingyuan, and Li Dong.
Lu Mingyuan was the first to speak.
He was holding an A4 sheet of paper, which contained the physical approach that Li Dong had just laid out.
"We’re going to pause the mathematical inversion approach we’ve been pursuing."
"We’re going to try this new direction first."
The room instantly erupted with murmurs.

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