Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Inorganic chemistry → Solid state chemistry ↓


Superconductors


Superconductors are fascinating materials with remarkable properties that have fascinated scientists and engineers alike since their discovery. They are a unique class of materials that exhibit zero electrical resistance and expulsion of magnetic fields below a certain temperature. This temperature is known as the critical temperature (Tc). The phenomenon of superconductivity was first discovered by Heike Kamerlingh Onnes in 1911 when he observed this feature in mercury at very low temperatures.

Basic concepts of superconductivity

At the core of superconductivity is the absence of electrical resistance, which otherwise causes energy loss as heat in normal conductor materials. In classical conductors such as copper or aluminum, electrons move through a lattice of metal ions. As they move, they collide with these ions and with each other, creating resistance. When this resistance is reduced to zero, as it is in superconductors, the electrons can travel through the material without losing energy.

Another important aspect of superconductivity is the Meissner effect, which describes the expulsion of magnetic fields from inside a superconductor as it transitions into the superconducting state. This effect not only makes superconductors perfect diamagnets but also enables phenomena such as magnetic levitation.

Historical context and discoveries

The journey to understanding superconductivity began with Heike Kamerlingh Onnes, who discovered this effect while measuring the electrical resistivity of mercury at graduated temperatures. This was revolutionary because it contradicted the prevailing understanding at the time that the resistance would decrease to a minimum value but would never reach zero.

In the following years, various elemental superconductors were discovered. Tin and lead were among the first elements whose superconducting state was identified. This led to the subsequent development of the theoretical understanding of superconductivity. It was not until 1957 that a comprehensive theory explaining superconductors was formulated by John Bardeen, Leon Cooper, and Robert Schrieffer, which was named BCS theory after their initials.

BCS principle

The BCS theory provides a microscopic explanation for superconductivity in conventional superconductors. It explains how electrons in a superconductor can form pairs known as Cooper pairs. Unlike individual electrons that repel each other due to their identical charges, Cooper pairs are formed due to their attraction mediated by lattice vibrations or phonons.

In the BCS theory, interactions between electrons result in a collective ground state that is energetically favorable, leading to a superconducting state. These Cooper pairs move through the lattice without scattering, leading to zero electrical resistance.

Cooper couple

Types of superconductors

Superconductors are divided into two main categories based on their superconducting behavior and physical properties: type I and type II.

Type I superconductor

Type I superconductors are typically fundamental superconductors that exhibit a complete Meissner effect - where all magnetic fields are expelled from the material. They have a fundamental behavior where the superconducting state is completely disrupted by a critical magnetic field. Examples of Type I superconductors include Tc = 4.15K for lead and Tc = 2.19K for tantalum.

Magnetic Field Superconductors Critical B

Type II superconductor

Type II superconductors are primarily complex metal alloys or high-temperature superconductors that partially allow magnetic fields to penetrate certain regions of the material. They have two critical magnetic fields, Hc1 and Hc2. Between these regions, the superconductor is in a mixed state where it excludes some magnetic fields and allows some to penetrate. Type II superconductors often have significantly higher critical temperatures and fields than Type I. Examples include niobium-titanium (NbTi) alloy and the well-known high-temperature cuprate superconductor, YBa2Cu3O7 (YBCO).

this hc1 hc2 Superconductors

High temperature superconductor

The discovery of high-temperature superconductors in the 1980s marked a turning point as it enabled the possibility of harnessing superconductivity at more feasible temperatures. High-temperature superconductors are materials that exhibit superconducting properties at significantly higher temperatures than conventional superconductors – sometimes even higher than the boiling point of liquid nitrogen (77 K).

The first high-temperature superconductor discovered was the barium-lanthanum-copper oxide compound YBa2Cu3O7 with a critical temperature of about 92 K. This success sparked a flurry of research activity and the discovery of other high-temperature superconductors, mainly based on copper oxides known as cuprates.

Applications of superconductors

Superconductors have many applications, mainly due to their unique electrical and magnetic properties. Some of their major applications are as follows:

Magnetic resonance imaging (MRI)

MRI machines, which rely heavily on superconductor technology, provide detailed images of organs and tissues in the human body. Superconducting magnets generate strong magnetic fields that help produce precise medical imaging without radiation exposure. The use of superconductors in MRI machines increases image resolution and reduces the operational costs of running these machines.

Maglev trains

Maglev, or magnetic levitation, trains move without touching the tracks, thanks to superconducting magnets that allow these trains to "float" above the tracks. This mechanism reduces friction, enabling the trains to achieve high speeds with exceptional energy efficiency.

Maglev Leverage

Power grids

Superconductors could substantially increase efficiency in power grids. By reducing or eliminating resistance, superconductors could reduce energy losses during power transmission. Such technologies could revolutionize energy distribution systems by facilitating long-distance transmission of electricity without any apparent losses.

Beyond their economic value, superconductors are crucial to advancing scientific research, making electromagnets for particle accelerators, and potentially providing a way to build quantum computers, which have unparalleled processing capabilities.

Challenges and future outlook

Despite the many advantages, there are challenges associated with the widespread implementation of superconductors. Maintaining the extremely low temperatures needed for superconductivity can be expensive and complex. More research is needed to develop new materials that can work as superconductors at higher, more manageable temperatures.

Ongoing research on room-temperature superconductors represents a promising horizon that could someday further revolutionize technology by eliminating the need for extensive cooling.

In conclusion, the field of superconductivity ties together many concepts from solid state and inorganic chemistry. It offers vast opportunities to advance technology in a variety of fields. By understanding and developing new superconducting materials, we contribute to transforming our energy systems, transportation networks, medical technologies, and much more.


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Superconductors

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