The Hidden World of Catalysts: From Electrons to Efficiency

Catalysts play a crucial role in advancing energy, environment, and material technologies for a sustainable future. Their magic often happens on complex, irregular solid surfaces where unique structures and electronic states drive activity. Sometimes, solvents or co-catalysts are also key players in the process. At the heart of understanding catalysts is theoretical chemistry. Even the most complex reactions boil down to simple principles rooted in electron behaviour and molecular motion, governed by fundamental equations like Schrödinger’s and Newton’s. By building theories from these, we can describe and predict chemical phenomena accurately. Computational chemistry brings these theories to life. It allows us to simulate invisible processes and measure properties that experiments can’t easily capture. Using advanced methods, such as QM/MM and ab initio molecular dynamics, we can peek into the details of catalytic reactions—from organic catalysts to metals—helping us design better materials and cleaner reactions for tomorrow.

Beyond the Test Tube: Why Theory and Computation Matter 

Why theories? Because experiments are how we discover Nature, they are our truth and something we can’t do without. We observe phenomena and get curious, but that’s just the beginning. Our minds naturally try to find patterns and make sense of what we see. When we do this systematically, we begin to uncover rules, general ideas that explain what’s happening. These rules become theories. Sometimes, we can express them using mathematics, which allows us to make predictions before conducting the next experiment. That’s where computations come in. Theoretical chemistry helps us in two ways: first, by finding the principles hidden in the experiments, and second, by using those principles to analyse and predict chemical behaviour. It’s like seeing the logic behind the beauty of chemistry. So why computations? Because they give us numbers, real, useful numbers that describe chemical systems. We observe reactions, we create new molecules, but it’s the numbers that help us understand them deeply. Computational chemistry lets us measure things virtually, energies, structures, interactions, that might be hard to capture in a lab. And once we have those numbers, it becomes easier to see the bigger picture, to connect the dots, and even to form new theories. It’s a different way of thinking, a new perspective. While experiments show us what happens, theory and computation help explain why, and sometimes even suggest what could happen next. And honestly, it’s fun. Something is exciting about using a computer to simulate Nature, to uncover truths, and to stretch your imagination. It’s a kind of thinking that opens up new paths, and anyone curious enough can walk them.

Theoretical and Computational Chemistry: Atoms, Algorithms, and Answers 

Theoretical and Computational Chemistry might sound complex, but at its core, it’s about using physics and math to understand how molecules behave. From quantum mechanics to thermodynamics, we use equations to explore reactions, bonds, and materials that are too small, too fast, or too reactive to observe directly in a lab. Instead of test tubes, we run simulations. Instead of spectrometers, we use Schrödinger’s equation. These tools let us see what’s normally invisible—how a catalyst works, how a drug fits into a protein, or how electrons flow through a battery material. But today, this field is evolving fast. Enter cheminformatics, machine learning, and artificial intelligence. With these tools, we can:

• Predict reaction outcomes

• Discover new materials for batteries, solar cells, and perovskites

• Accelerate drug design by screening millions of molecules

• Understand how biological systems respond to small molecular changes

For example, deep learning models can now predict the structure and energy of molecules in seconds—a task that once took days of quantum calculations. And machine learning-guided simulations are helping us understand enzymes, design better catalysts, and build more efficient materials. This isn’t replacing theory—it’s expanding its reach. By combining traditional quantum chemistry with AI and data-driven insights, we can tackle challenges across biology, energy, environment, and medicine. So while the tools may have changed, the mission is the same: to explore the hidden world of molecules, and use that knowledge to design the future—one atom, one bond, one algorithm at a time.

Soft but Strong: Hydrogen Bonds in H₂S–Water Clusters

We’ve already explored how hydrogen bonds behave in hydrogen fluoride–water, methanol–water, and ammonia–water clusters. Now, we turn to hydrogen sulfide (H₂S) and see how it interacts both with itself and with water. Using the molecular tailoring approach, we looked at different hydrogen bonds that form in pure H₂S clusters and mixed H₂S–water clusters. The bonds involving water tend to be stronger, especially when water donates a hydrogen to H₂S. In contrast, bonds where H₂S donates to another H₂S are much weaker, reflecting sulfur’s softer, less electronegative nature compared to oxygen. An important finding is how these bonds work together. Just like in our earlier studies, cooperativity plays a key role: the presence of one hydrogen bond can make nearby bonds stronger. In mixed clusters, this cooperative effect boosts the overall stability and shows how water helps "organise" the bonding network. Understanding how H₂S interacts with water gives insight into chemical behaviour in natural and biological systems where sulfur compounds are present. Even though H₂S forms weaker bonds than water, its contribution to hydrogen-bonded networks is still significant, especially when teamwork comes into play.

A Tug of War: Hydrogen Bonds in Ammonia-Water Clusters

We’ve seen hydrogen bonds in hydrogen fluoride and methanol-water clusters before. Now, we study what happens when ammonia joins water in clusters. In these mixed clusters, hydrogen bonds form between water and ammonia as well as within each group. Our study shows that the strongest bonds happen when water’s OH group donates hydrogen to ammonia’s nitrogen (OH...N). These bonds can be quite strong, much stronger than bonds where ammonia donates hydrogen or where water bonds to itself. Interestingly, the bond strengths don’t just add up—they influence each other through a phenomenon called cooperativity. This means one strong bond can boost the strength of nearby bonds, making the whole cluster more stable. Why does this matter? Understanding these mixed hydrogen bonds helps us predict how ammonia-water mixtures behave in chemistry and biology. It also guides the better design of solvents and materials where these interactions play a big role. Our work adds to previous studies by revealing how the tug of war between self- and cross-associating hydrogen bonds shapes the cluster’s energy and structure. Small bonds working together create big effects, just like teamwork makes the dream work at the molecular level.

How Hydrogen Bonds Work in Methanol-Water Clusters 

In our previous blogs, we explored the unique nature of hydrogen bonds in water, ammonia, and hydrogen fluoride clusters. Now, turning to methanol-water mixtures, we see a different but equally interesting story. Using the molecular tailoring approach, we studied how various hydrogen bonds behave in methanol-water clusters. We found that the strongest hydrogen bonds occur when the oxygen in methanol donates a hydrogen to the oxygen in water. These bonds range from about 7 to 12 kcal/mol. Bonds between two methanol molecules follow closely behind, while the weakest bonds are generally those where water donates hydrogen either to water or to methanol. This ordering is different from what we observe in simple pairs of molecules (dimers). The reason is the complex interplay of cooperative and anti-cooperative effects within the hydrogen bond network. Cooperativity can strengthen bonds by 1 to 8 kcal/mol, changing the energy landscape in these clusters. This means that hydrogen bonds in methanol-water mixtures don’t just add up individually but influence each other’s strength in subtle ways. Understanding this helps us better predict how mixed solvents behave in chemical and biological systems. Together with our earlier findings on water, ammonia, and hydrogen fluoride, this work highlights the delicate balance of forces behind hydrogen bonding and the importance of considering the entire network rather than isolated pairs. 

Stronger Together: Hydrogen Bonds in HF-Water Clusters 

We have studied hydrogen bonds in water, ammonia, and hydrogen fluoride before. Now, we look at what happens when HF and water molecules form clusters together. In these mixed clusters, HF and water molecules connect through hydrogen bonds in ring-like structures. The bonds where HF donates hydrogen to water are the strongest, sometimes more than twice as strong as the bonds where water donates hydrogen. Other types of bonds, like water donating hydrogen to fluorine, are weaker but still important. A key finding is about cooperativity, which means that the presence of one hydrogen bond makes the nearby bonds stronger. This teamwork between bonds adds significantly to the overall stability of the clusters. Why is this important? Understanding these hydrogen bonds helps us explain how molecules interact in many areas, such as solvents, chemical reactions, materials science, and biology. It also supports better design of materials for batteries, catalysts, and drugs. This study builds on our earlier work on water, ammonia, and HF by showing how mixing molecules creates new, stronger hydrogen bond networks. Small bonds working together make a big difference in how molecules behave.

The Hidden Power of Hydrogen Fluoride  

Hydrogen fluoride (HF) may be a small molecule, just one hydrogen and one fluorine, but when it comes to hydrogen bonding, it’s anything but weak. Like water and ammonia, HF molecules don’t stay isolated for long. They link up through hydrogen bonds, those invisible threads that hold matter together and shape chemistry at every level. But HF has a unique twist: fluorine is one of the most electronegative elements, and that makes its hydrogen bonds remarkably strong, stronger than those in water or ammonia. When HF molecules cluster together, their hydrogen bonds don’t just stack, they cooperate. That’s right: one bond actually makes the next one stronger. This cooperativity is like molecular teamwork, and it becomes especially pronounced in cyclic HF clusters. In our ongoing exploration of hydrogen bonding, from water, to ammonia, and now HF, we’ve used theoretical chemistry to break down molecular clusters and evaluate each individual bond. Our recent study on HF, using the molecular tailoring approach, revealed just how much these small interactions grow stronger through collective behaviour. In fact, a big chunk of the bonding strength in HF clusters doesn’t come from the bond itself—it comes from how it interacts with its neighbours.

Weak Bonds, Big Impact: Ammonia Clustering  

Hydrogen bonds are everywhere, quiet, invisible forces that hold molecules together and shape how matter behaves. We often hear about them in water, but ammonia? That’s a less talked about story. Ammonia, a simple molecule with one nitrogen and three hydrogens, forms its own network of hydrogen bonds, just like water. These bonds, though individually small, combine to create something surprisingly strong. Even more fascinating, when ammonia molecules cluster, these bonds help each other, called cooperativity, like teamwork at the molecular level. Building on the story we began with water, we recently explored ammonia’s subtle yet intriguing bonding. By analysing ammonia clusters piece by piece, we measured how much each hydrogen bond contributes. This isn’t just theory, ammonia is a key solvent where water can’t do the job. Understanding its bonding helps scientists design better reactions, predict structures, and improve simulations. The strength and teamwork of ammonia’s hydrogen bonds reveal a rich story, reminding us again how the smallest connections can unlock the biggest mysteries.

The Secret Strength of Water 

Water is simple, yet endlessly fascinating. We know it flows, evaporates, freezes, but behind all this is a hidden world of weak interactions. The real magic lies in how one water molecule bonds to another through what we call hydrogen bonds. These aren’t the strong, rigid bonds you find inside molecules; they're softer, more flexible, like invisible handshakes between neighbours. And when several water molecules gather, they form complex, shifting networks held together by these bonds. But here's something you might not have noticed: not all hydrogen bonds in water are equal. Some are stronger than others. And as more molecules join in, each bond can actually get a little boost from its surroundings, something called cooperativity. It’s like a team dynamic, where one member helps the others perform better. Until recently, we couldn’t really say how strong each individual hydrogen bond was. We knew they mattered, we just couldn’t give them a voice. But now, with the right approach, we can start to "hear" each bond's contribution. We found that some bonds in water clusters can be surprisingly strong, even comparable to those in well-known chemical interactions. Others are gentler, but no less important. Together, they create a subtle balance that gives water its unique power, its ability to shape life, weather, and so much more. All of this from the quiet forces between molecules. It’s a small continuation of the story we started in our earlier blog, The Story of Hydrogen Bonds, where we explored a century of hydrogen bonding, from its 1912 origins in aqueous amines to its starring role in biology and materials science today. And it’s a reminder that sometimes, the smallest connections carry the biggest stories.