Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → Inorganic chemistry → Solid state chemistry ↓


Superconductivity


Superconductivity is a fascinating phenomenon observed in certain materials where they exhibit zero electrical resistance and expel magnetic fields when they are cooled below a specific critical temperature known as the superconducting transition temperature. This property allows the uninterrupted flow of electrical current. Superconductivity has attracted significant attention due to its potential to revolutionise energy transmission, magnetic levitation and quantum computing.

Discovery of superconductivity

The phenomenon of superconductivity was first discovered by Heike Kamerlingh Onnes in 1911. Onnes observed that when mercury was cooled to temperatures close to absolute zero (about 4.2 Kelvin or -268.95 °C), it had no electrical resistance. This discovery was groundbreaking because it challenged the conventional understanding of electricity and conductivity at the time.

When a material transitions into a superconducting state, it enters a state of perfect diamagnetism, meaning it repels magnetic fields completely. This aspect of superconductors is explained by the Meissner effect, discovered by Walther Meissner and Robert Ochsenfeld in 1933.

Fundamentals of superconductivity

The understanding of superconductivity depends on several key principles:

Zero electrical resistance

In ordinary conductors such as copper or silver, electrons collide with atoms and impurities, resulting in resistance. This resistance generates heat and energy loss. However, in a superconductor, electrons form pairs known as Cooper pairs. These pairs move through the lattice structure of a material without scattering, thereby eliminating electrical resistance.

Meissner effect

The Meissner effect describes the expulsion of magnetic fields from within a superconductor. As a material transitions into its superconducting state, the internal magnetic field drops to zero, ensuring perfect diamagnetism.

B

This SVG shows a schematic diagram of the Meissner effect, where B (magnetic field lines) are expelled from a superconducting sphere.

Types of superconductors

Superconductors can be broadly classified into two categories:

Type I superconductor

These are usually native elemental superconductors, such as lead, tin, and mercury. Type I superconductors exhibit a perfect Meissner effect and transition to a superconducting state at a single critical magnetic field. If the magnetic field exceeds this critical value, superconductivity is destroyed.

Type II superconductor

Made from alloys and high-temperature ceramic compounds, Type II superconductors enter a mixed state known as the "vortex state." This occurs between two critical points: the lower critical field and the upper critical field. In this state, magnetic field lines partially penetrate the material, forming vortices. Type II superconductors can maintain superconductivity under higher magnetic fields than Type I.

Applications of superconductivity

The unique properties of superconductors have opened the door to a range of technological applications:

Magnetic levitation

Superconductors are used in magnetic levitation (maglev) transportation systems, in which trains float above tracks, eliminating friction and achieving higher speeds and energy efficiency.

Energy storage and transmission

Superconducting materials are used for lossless energy transmission in power grids, and are also used in superconducting magnetic energy storage (SMES) systems, which store energy with high efficiency.

Quantum computing

The building blocks of quantum computers, superconducting qubits, use the quantum state symmetry of superconductors to perform calculations far more efficiently than conventional computers.

Challenges and future prospects

Despite their promise, superconductors face significant challenges. The main obstacle is the low critical temperature needed to achieve superconductivity. High-temperature superconductors discovered in the late 1980s partially solve this problem, but the need for expensive cryogenic systems limits widespread use.

Ongoing research is aimed at discovering new materials and mechanisms to achieve superconductivity at room temperature, which will revolutionize electronics, power systems, and many other industries.

Chemical aspects of superconductivity

The study of superconductors often extends beyond their physical properties to include chemical aspects as well. This includes composition, bonding, and crystal structure, which affect the superconducting transition temperature and other properties.

Transition metal oxides

Many high-temperature superconductors are copper oxides with complex structures and chemical compositions. These CuO 2 planes are integral to their superconducting properties.

Intermetallic and alloy superconductors

Alloy superconductors, such as niobium-tin (Nb 3 Sn), feature mixed metallic bonding and an ordered structure, which affect their superconducting transition temperature.

This SVG represents the intermetallic bonding within the unit cell of an alloyed superconductor.

Theoretical background

The theoretical study of superconductivity involves understanding the electron pairing and interaction with the crystal lattice:

BCS principle

The Bardeen-Cooper-Schrieffer (BCS) theory, formulated in 1957, describes classical superconductors. It assumes that electrons form Cooper pairs by exchanging via lattice vibrations called phonons. These pairs condense into a ground state where the resistance is zero.

Ψ = √N₀ exp(iθ)

The wave function Ψ represents a coherent state with intact symmetry, which is responsible for the superconducting phase.

The way forward

Superconductivity remains an area of intense scientific exploration, bridging chemistry and physics. Advances in the understanding of high-temperature superconductivity, novel materials, and improved synthesis methods will lead to further applications.

Researchers are committed to overcoming challenges such as creating defect-free, large-scale superconductors and understanding the interaction mechanisms between them. With continued dedication and collaboration across disciplines, the future of superconductivity is bright.


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Superconductivity

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