UNDER MORE PRESSURE (C)1999 Alan M. Schwartz When you squeeze stuff things happen, especially if there are denser states in the offing. Give things a squeeze (like 16,200 psi at the 36,200-foot deep Marianas Trench bottom), sea level biochemistry fails (benthic locals cannot live at the surface), and water freezes at -10 C. At 30,000 psi water freezes at -17 C; 205,000 psi gives 50 C; and at 536,000 psi water freezes at 175 C. Give quartz a squeeze and get coesite (305,000 psi), then stishovite (1.1 million psi; both persist metastable at ambient conditions). The paradigm is a straightforward: find a crystal structure that is not atomically dense, notably whose atoms are multiply bonded, and ram them into each other graphite (2.25 g/cm^3) to diamond (3.51 g/cm^3). Push come to shove the crystal lattice contracts, valence electrons smear, and you get something different with which to apply for more research grants. Silicon dioxide (quartz) is one big covalently bonded molecule, hence its hardness, high melting point (1600 C), and large melt viscosity (things stay attached and tangle over large distances). Each silicon is tetrahedrally bonded to four oxygens. Carbon dioxide is linear O=C=O whose crystals contain isolated molecules at large separations. Dry Ice is soft, sublimes at -78 C, and liquid CO2 has a lower viscosity than water (Int. J. Thermophys. 15 767 (1994)). There is no a priori reason why a chemist could not build a crystal of "carbon dioxide" with the quartz structure, carbon substituting for silicon. The problem is getting there kinetically without making the plebeian stuff, or motivating things thermodynamically which requires a big squeeze indeed. Dry Ice loiters at the bottom of a deep hole. You cannot tour the energy hypersurface until you climb out. Science 284(5415) 788 (1999) explores a theoretical big squeeze onto solid CO2 (Dry Ice). Things get interesting above 1.6 million psi when the cubic Pa3 structure (alpha-CO2) slightly compacts to orthorhombic Cmca (beta-CO2). Things really get interesting at 19 million psi and 730 C when individual molecules merge into two-dimensional planes of four-coordinate carbon and volume shrinks by 9% to give the boojum - a tetrahedral CO4-based structure of space group P43/nmc. At 1700 C a fully three- dimensional CO4-based structure analogous to quartz results, in theory. Other people think so too - Science 283 1510 (1999). So? Those hellish conditions (beyond white hot at 23 times the pressure needed to grow diamonds) are only fleetingly achievable in the microscopic volume of a diamond anvil press or transiently macroscopically in a high explosive multiply-staged and tampered implosion. Both cases sincerely push the performance envelope. When things go bad diamond anvils crack at maybe $50,000 each. Implosion will easily do hundreds of grams, but how do you cool the anomalous product into metastability before everything glowing white-hot rebounds? The experiment is simple and cheap. Implode away! Chemical approaches might do it in a flask stirring under the supervision of a desperate graduate student. C(OR)4 species are not unknown. Polycyclic orthocarbonates are reactive monomers that expand volumetrically (compact rings opening into floppy linear structures) upon acid or free radical initiation. Ordinary polymerizations contract, small molecules assembling into big ones and squeezing out interstitial space. How to build a dendrimer polymer of orthocarbonate without internal prosthetic chemical functionality or external collapse to soda bubbles is left as an exercise for the alert reader. Aside from curiosity, is there any reason to commit vast time, personnel, and materiel resources to will-'o-the-wisp pure research? Sure! Carbon dioxide is the overweening hobgoblin of the nugatory Greenhouse Effect Officially threatening to transmute overall cool and dry Gaia into an abhorrent Garden of Eden thickly carpeted with warm, moist forests and incredibly productive farmlands. Environmentalists demand unlimited diversion of First World national resources to sequester CO2 from the atmosphere lest the Third World not get its fair share of slash and burn agriculture or nightly cooking fires exacerbating local deforestation. (Let us not be unfair here. Third World denizens also burn dried dung for fuel, assuring their soils remain rocky and infertile.) Storing annual gigatonnes of high pressure (838 psi/70 F) liquid CO2 is a real challenge given international terrorist threats and the ready availability of can openers despite frantic Federal legislation to control unauthorized access. Damn the canned goods lobby! Conversion of harmless gaseous CO2 through an inconceivably expensive energy-intensive process into a monstrously dangerous solid slated for mass landfill is entirely reasonable, certainly for funding preliminary studies. If not us, who? If not now, when? Do you want to kill every child on Earth or will you sustain Environmentalist caprice? You will feel pressure but no pain. Gardyloo! I mean, GardyCO2!