Carbon is an element with extremely versatile bonding properties and theoretical calculations have suggested the possible existence of several hundred structural allotropes. Many, or even most, of these are predicted to be formed under conditions of high pressure and temperature. On the other hand, experimental high pressure studies have identified surprisingly few structural allotropes. In this paper, physical properties and structural transformations observed in high pressure experiments, at and above room temperature, are reviewed for a large number of solid carbon allotropes. The materials discussed include bulk carbon such as graphite, diamond, glass-like and amorphous carbon, two-dimensional graphene, and molecular carbon in the form of one-dimensional carbon nanotubes and zero-dimensional fullerenes. Results from recent studies on twisted graphene, graphdiyne, graphyne, carbon dots and other interesting all-carbon allotropes are also briefly described. Observed similarities and differences between the high pressure behavior and evolution of carbon materials are discussed. In spite of the enormous volume of experimental work carried out on these materials, few new structural allotropes have been identified and most carbon materials studied convert into diamond at sufficiently high temperature and pressure. Further theoretical work thus seems to be needed to elucidate possible transformation processes and transition paths for the many undiscovered allotropes proposed from calculations. In particular, it is recommended that, for every new allotrope predicted by theory, suitable precursors and transformation conditions should also be investigated. Efficient creation of new structural allotropes or functional materials based on pure carbon by high pressure methods should ideally start from designed, preassembled precursor structures or composites for which transition paths can be theoretically predicted.

碳是一种具有极其广泛的键合特性的元素，理论计算表明可能存在数百种结构同素异形体。预计其中许多甚至大多数是在高压和高温条件下形成的。另一方面，实验性高压研究发现令人惊讶的是很少有结构同素异形体。本文综述了在室温及高于室温的高压实验中观察到的物理性质和结构转变，以分析大量的固态碳同素异形体。讨论的材料包括散装碳，例如石墨，金刚石，类玻璃和无定形碳，二维石墨烯和一维碳纳米管和零维富勒烯形式的分子碳。还简要介绍了有关扭曲石墨烯，石墨二炔，石墨烯，碳点和其他有趣的全碳同素异形体的最新研究结果。讨论了高压行为和碳材料的演化之间观察到的异同。尽管对这些材料进行了大量的实验工作，但几乎没有发现新的结构同素异形体，大多数研究的碳材料都在足够高的温度和压力下转化为金刚石。因此，似乎需要进一步的理论工作来阐明计算中提出的许多未发现的同素异形体的可能转变过程和转变路径。特别是，建议对于理论预测的每种新同素异形体，还应研究合适的前体和转化条件。