Accidental synthesis of a previously unknown quasicrystal in the first atomic bomb test

Accidental synthesis of a previously unknown

quasicrystal in the first atomic bomb test

Luca Bindi

a,1



, William Kolb

, G. Nelson Eby



, Paul D. Asimow



, Terry C. Wallace



, and Paul J. Steinhardt

f,1

Dipartimento di Scienze della Terra, Università di Firenze, I-50121 Firenze, Italy;

2702 Church Creek Lane, Edgewater, MD 21037;

Department of

Environmental Earth and Atmospheric Sciences, University of Massachusetts, Lowell, MA 01854;

Division of Geological and Planetary Sciences, California

Institute of Technology, Pasadena, CA 91125;

Los Alamos National Laboratory, Los Alamos, NM 87545; and

Department of Physics, Princeton University,

Princeton, NJ 08544

Contributed by Paul J. Steinhardt, April 6, 2021 (sent for review February 8, 2021; reviewed by Peter C. Burns and Christopher Hamann)

The first test explosion of a nuclear bomb, the Trinity test of 16

July 1945, resulted in the fusion of surrounding sand, the test

tower, and copper transmission lines into a glassy material known

“

trinitite.

”

Here, we report the discovery, in a sample of red

trinitite, of a hitherto unknown composition of icosahedral quasi-

crystal, Si

. It represents the oldest extant anthropo-

genic quasicrystal currently known, with the distinctive property

that its precise time of creation is indelibly etched in history. Like

the naturally formed quasicrystals found in the Khatyrka meteor-

ite and experimental shock syntheses of quasicrystals, the anthro-

pogenic quasicrystals in red trinitite demonstrate that transient

extreme pressure

–

temperature conditions are suitable for the syn-

thesis of quasicrystals and for the discovery of new quasicrystal-

forming systems.

quasicrystals

|

trinitite

|

atomic bomb

|

Khatyrka

|

shock

he Trinity test

—

the detonation of a plutonium implosion

device known as the

“

gadget

”—

occurred at 05:29:45 Moun-

tain War Time on 16 July 1945 on the Alamogordo Bombing

Range, about 210 miles south of Los Alamos, NM. The explosion

released the equivalent of 21 kilotons of TNT (88 TJ), sufficient

to vaporize the 30-m test tower and surrounding miles of copper

wires to recording instruments. The explosion produced a large

fireball that entrained arkosic sands that rained out as fused crusts

and droplets that are now known as trinitite (1

–

3). We present

here evidence of an unintended consequence: the synthesis of a

novel icosahedral quasicrystal (empirical formula Si

The grain (about 10

m across) was discovered in a copper-rich

droplet included in a sample of red trinitite recovered shortly after

World War II. This is evidence that the high-temperature, high-

pressure conditions created by a nuclear explosion can, like the

transient conditions induced by hypervelocity impact in the Khatyrka

meteorite (4

–

8), result in the synthesis of quasicrystals.

The Trinity test created a crater about 1.4 m deep and 80 m

wide, vaporizing the experimental infrastructure and fusing the sur-

face sands to a depth of 1 to 2 cm out to a radius of about 300 m. As

first reported by Ross (9), triniti

te glass was formed by fusing the

sand, consisting mostly of quartz and feldspar, and most often is

characterized by a pale green color. Later work (1

–

3) has shown that

most of the trinitite formed from

sand that was swept up in the fire

ball and subjected to the high temperatures and pressures (about

1,500 °C and pressures of 5 to 8 GPa, as explained in

Discussion

)of

the developing cloud, subsequently raining out as glass and fusion

crust fragments. Although the vast majority of the trinitite is the

classic

“

green

”

color, there are numerous fragments characterized as

“

red

”

trinitite that are typically rich in metals derived from the test

tower and recording equipment.

Results

The trinitite sample investigated in this paper is an example of

the rarer oxblood red trinitite (Fig. 1) that Ross (9) reported finding

north of the test site, where it was recovered by Lincoln LaPaz just a

few months after detonation (3).

The red color is attributed to the presence of copper oxide

(10) that formed when the copper transmission lines were va-

porized. Based on the detection of gamma rays associated with

the decay of

152

Eu in our sample, the red trinitite appears to have

been created about 55 to 60 m from ground zero, close to where

the coaxial cable from the top of the tower terminated in a trench.

Red trinitite is composed of remnant quartz and feldspar

grains which have partially melted to glasses of similar chemistry;

Al-Ca-K silicate, Ca-Al silicate, Ca-Al-Fe silicate, and Fe-Ca-Al

silicate glasses; and metallic phases comprising 3 to 5% of the

material (10). The samples are usually heterogeneous mixtures at

the 10- to 100-

m scale. Metallic inclusions (spherules) are com-

mon in red trinitite. These include Cu-Pb-Fe and Cu-Fe spherules

which frequently show immiscibility and unmixing textures. Fe-Si,

Fe-Ti, Cu-S, PbO spherules, and a single grain of a W-Ga-Ta alloy

have been found (10). Fig. 2,

Left

shows a back-scattered scanning

electron microscope image of the surface of the red trinitite

sample after it was embedded in epoxy and polished. X-ray maps

of the polished surface, shown in Fig. 2,

Right

, indicate the Ca-Si-Al

chemical compositional variation. The focus of this paper, though, is

on the metallic rounded droplet encircled in Fig. 2, which is em-

bedded in a Na-bearing Al-Ca-K silicate glass (

SI Appendix

,Fig.S1

and Table S1

Fig. 3 zooms in on the droplet and shows a back-scattered

scanning electron microscope image. The X-ray maps on the right

make clear that the droplet is copper-rich, a characteristic of many

of the metal droplets in red trinitite (10). Of the dozen or so copper

Significance

This article reports the discovery of a heretofore unknown

icosahedral quasicrystal created by the detonation of the first

nuclear device at Alamogordo, NM, on 16 July 1945 (the Trinity

test). Like all quasicrystals, the new example violates crystal-

lographic symmetry rules that apply to ordinary (periodic)

crystals. It was found in a sample of red trinitite, a combination

of glass fused from natural sand and anthropogenic copper

from transmission lines used during the test. The new quasi-

crystal is the oldest extant anthropogenic quasicrystal known,

whose place and moment of origin are known from the historic

records of the Trinity test. The thermodynamic/shock condi-

tions that formed it are roughly comparable to those that

formed natural quasicrystals recently found in meteorites.

Author contributions: L.B., P.D.A., and P.J.S. designed research; L.B. performed research;

L.B. and P.D.A. analyzed data; L.B., W.K., G.N.E., P.D.A., and P.J.S. wrote the paper; W.K.

contributed samples; and T.C.W. contributed to the paper.

Reviewers: P.C.B., University of Notre Dame; and C.H., Museum für Naturkunde Berlin.

The authors declare no competing interest.

Published under the

PNAS license

To whom correspondence may be addressed.

Email: luca.bindi@unifi.it or steinh@

princeton.edu.

This article contains supporting information online at

https://www.pnas.org/lookup/suppl/

doi:10.1073/pnas.2101350118/-/DCSupplemental

Published May 17, 2021.

PNAS

2021 Vol. 118 No. 22 e2101350118

https://doi.org/10.1073/pnas.2101350118

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droplets studied in this sample, though, this droplet is unique in

that, in addition to the familiar chalcocite (Cu

S), it contains a

mostly Si-Cu-Ca phase (about 10

m in diameter) that has not

been reported previously. The average of four electron micro-

probe analyses yields a composition of Si 42.86(80), Cu 47.70(85),

Ca 6.80 (26), Fe 2.65 (19), total 99.80 wt %, corresponding, on the

basis of a total of 100 atoms, to Si

This new phase was extracted and mounted for single-crystal

X-ray diffraction. Fig. 4 shows the projections of the single crystal

X-ray diffraction data for the Si

sample formed

during the Trinity test along the fivefold (Fig. 4,

Top

), threefold

(Fig. 4,

Middle

), and twofold symmetry axes (Fig. 4,

Bottom

) that

define the symmetry of an icosahedron. The combination of pat-

terns demonstrates unambiguously that the new phase is an ico-

sahedral quasicrystal, the first to be identified in the remnants of

an atomic blast.

Discussion

Quasicrystals, as first introduced by Levine and Steinhardt (11),

are defined by a quasiperiodic distribution of atoms arranged in

a pattern that violates the crystallographic symmetry rules that apply

to ordinary (periodic) crystals. The

first report of an icosahedral alloy

was by Shechtman et al. (12), who described a metastable phase of

Al and Mn. Since then, over a hundred other quasicrystal com-

positions have been identified that have icosahedral symmetry or

other symmetries forbidden to periodic crystals, such as 8-, 10-,

or 12-fold symmetry (13, 14). Many have a thermodynamic sta-

bility field on the liquidus (13).

The icosahedral Si

phase reported here is unique

in several respects. It has been discovered first in the fused

remnants from an atomic blast and has yet to be synthesized in

the laboratory. In fact, there are currently no other known com-

positional mixtures of Si, Cu, and Ca of any type that have been

shown to be quasicrystalline, nor is there any other currently

known quasicrystal that is dominantly composed of Si. Ca-bearing

quasicrystals containing Au or rare earth elements have been

reported (13, 14), but none containing Cu or Si.

The icosahedral Si

phase is also the oldest extant

anthropogenic quasicrystal known. The first reported example of

a laboratory-synthesized icosahedral phase or a quasicrystal of

any type is the spin-quenched sample of Al

Mn described by

Shechtman et al. in 1984 (12). Bradley and Goldschmidt (15)

studied the X-ray powder diffraction patterns of the stable phases

of Al-Fe-Cu alloys that included a phase

, which was shown 50 y

later to be a stable icosahedral quasicrystal phase (16). However,

in 1939, Bradley and Goldschmidt (15) could not determine the

symmetries of the

phase from their powder data and the original

samples do not exist for verification. Other known near-misses for

discovery of the first quasicrystal (13, 14) include phases studied by

Hardy and Silcock (17), Palenzona (18), and Bruzzone (19), whose

alloys were later resynthesized and found to be quasicrystalline.

Unlike the other historic examples, the icosahedral quasicrystal

phase reported here exists and its symmetries can be verified to-

day. Furthermore, because of its unique mode of creation, its time

of synthesis is known to within a few seconds. Although we do not

know if this composition of icosahedral quasicrystal is thermo-

dynamically stable or metastable, it has persisted in the quasi-

crystalline state for 75 y. The only known examples of older

quasicrystals are the naturally formed quasicrystals discovered in

the Khatyrka meteorite that date back at least hundreds of mil-

lions of years and perhaps to the beginning of the Solar System (6,

–

23). Curiously, neither the oldest extant natural nor the oldest

extant anthropogenic quasicrystal was made under controlled

laboratory conditions.

Although the maximum instantaneous temperature reached

during the Trinity test may have been as high as 8,000 °C, Eby

et al. (10) present mineralogical and chemical data indicating that

trinitite formed at temperatures of about 1,500 °C and pressures of

5 to 8 GPa. Since Si

has not yet been synthesized in

the laboratory, it is not known if a stability field exists and, if so,

over what temperature

–

pressure range. Coincidentally, the

temperature

–

pressure range estimated for red trinitite is com-

parable to what was reported (21) in the study of the high-velocity

impact shock experienced by the Khatyrka meteorite (about 1,200

°C and

>

5 GPa), which

—

given a completely different mix of

Fig. 1.

Incident light images of the red trinitite sample (front and back of

the sample).

Fig. 2.

General back-scattered scanning electron microscope image of the

polished surface of the sample studied (

Left

). The small bright grain enclosed

in the red dashed circle is enlarged in Fig. 3. Combined X-ray maps (

Right

)of

the same portion of the sample.

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starting materials

—

led to the formation of quasicrystals with

completely different compositions. Inspired by Khatyrka, Asimow

et al. (24) performed a series of plate impact shock recovery ex-

periments at somewhat lower temperatures (about 400 °C) and

higher pressures (14 to 21 GPa) that led to the formation of

quasicrystalline alloys similar to those in Khatyrka. However, in

the case of Al-dominant shock-synthesized quasicrystals in Kha-

tyrka and in experiments, reduced Al metal was already present in

the starting materials. Metallic Cu was also present as well as both

oxidized and metallic Fe; Oppenheim et al. (25) showed that

metallic Fe precursor was apparently necessary for the synthesis.

The Si-dominant quasicrystal in the trinitite case differs in that the

original source of the major element, Si, was in oxidized form as

quartz or plagioclase in the sand at the test site. Reducing Si is

challenging, but it occurs in shock and release events, both at very

high temperatures according to thermodynamic calculations (26)

and at moderate temperatures at metal

–

silicate interfaces in

recovery experiments (27), even in the absence of strong reducing

agents. We emphasize that at this time we do not know the detailed

Fig. 3.

Back-scattered scanning electron microscope image of the studied

metal droplet (

Top

) containing the quasicrystalline phase. X-ray maps of the

same area are shown below.

Fig. 4.

Reconstructed precession images along the fivefold (

Top

), threefold

(

Middle

), and twofold symmetry axis (

Bottom

) obtained using the collected

single-crystal X-ray dataset (Mo

radiation) on the extracted quasicrystalline

fragment.

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sequence of events that led to the formation of a reduced Si-

bearing quasicrystal included in a Cu-Cu

S droplet embedded in

red trinitite. Forensically demonstrating that it is present is a first

step; further detailed work toward a mechanistic understanding

of its origin must consider the various thermodynamic and ki-

netic processes that may have occurred along possible pathways

through time, temperature, pressure, and oxygen fugacity in the

nuclear test environment.

The plate impact shock experiments, the high-velocity mete-

oroid shock impacts, and now an atomic blast shock event have

not only led to the formation of icosahedral quasicrystals, but

also each case has formed quasicrystal phases that were previ-

ously unknown, despite over three decades of systematic labo-

ratory synthesis searches. These findings suggest that examining

the remnants of these and other shock phenomena may prove to

be surprisingly successful in identifying new quasicrystal-forming

compositions and studying their kinetic stability. One reason may

be that the shock phenomena often mix four or more elements in

combinations not normally explored in the laboratory and qua-

sicrystals may be more common when there are more components

(25, 28). Also, for some quasicrystals, such as those in the Al-Fe-Cu

alloy system (29), the stability field is known to be enlarged under

static high-pressure conditions. It remains to be seen if the newly

discovered icosahedral Si

phase can be synthesized

under ordinary laboratory conditions and what its thermodynamic

stability field may be.

The work presented here thus motivates several new direc-

tions of research. Studying remnants from other nuclear test sites

may yield yet other novel quasicrystalline phases and, by un-

derstanding their thermodynamic properties, provide a new tool

for nuclear forensics. Fulgurites resulting from lightning strikes

(30) may be a source of either natural or semianthropogenic

quasicrystals depending on what materials are struck. Material

from Meteor Crater and other meteor impact structures as well

as some tektites (31) and lunar surface samples (32) provide

further sources of material that experienced comparable high-

temperature, short-duration shock events. All of these may be

useful for discovering new quasicrystal phases, shedding light

on why quasicrystals form, and learning how ubiquitous

they are.

Materials and Methods

Samples.

The red trinitite sample described in this paper and shown in Fig. 1 is

one of six samples of roughly the same size examined for this study, all of which

were provided by one of the authors (W.K.) and are among samples collected in

late 1945 by Lincoln LaPaz from a location north of ground zero. Red (rather

than green) trinitite samples were s

elected because they were reported

by Eby et al. (10) to incorporate blobs with rich inhomogeneous combi-

nations of metallic phases (most cu

rrently known quasicrystals are

metallic alloys).

The samples were embedded in epoxy resin and prepared as polished thick

sections. Twelve metallic blob candidates that appeared promising in terms of

chemical composition and suitable size for being tested by single-crystal X-ray

diffraction were removed by hand (using fine needles) from the polished

sections. Each was about 20

m across. All grains were found to have rela-

tively good diffraction quality: Eight turned out to be cubic, three hexago-

nal, and one icosahedral (quasicrystal), the last of which is the subject of this

paper. Even in hindsight we cannot identify characteristics that allow one to

distinguish the quasicrystals from crystals without diffraction data; finding

more samples relies on systematic search.

The results presented here are from scanning electron microscopy, elec-

tron microprobe, wavelength-dispersive spectrometry (WDS), and single-

crystal X-ray diffraction techniques.

Radioactivity Measurements.

The sample was measured on a 5-inch NaI(Tl) well

detector to estimate the Eu-152 and Cs-137 content. The 4-g sample contained

∼

6 Bq of Eu-152 and 100 Bq of Cs-137 which are typical in red trinitite. Eu-152

is a soil activation product and gives an indication of the distance from ground

zero (33). The specific activity in this sample is consistent with trinitite found 55

to 60 m from the explosion hypocenter.

Scanning Electron Microscopy.

The instrument used was a Zeiss EVO MA15

scanning electron microscope coupled with an Oxford INCA250 energy-

dispersive spectrometer, operating at 25 kV accelerating potential, 500-pA

probe current, 2,500 counts per second as average count rate on the whole

spectrum, and a counting time of 500 s. Sample was sputter-coated with

30-nm-thick carbon film.

Electron Microprobe.

Quantitative analyses were carried out using a JEOL

JXA 8200 microprobe (WDS mode, 15 kV, 10 nA, 1-

m beam size, counting

times 20 s for peak and 10 s for background). For the WDS analyses the

lines for all the elements were used. The quasicrystal fragment was

found to be homogeneous within analyt

ical error. The standards used

were Si metal, synthetic CaSi

(Ca), Cu metal, and Fe metal. Four point

analyses on different spots on the single reported

∼

10-mm quasicrystal

were collected.

Single-Crystal X-Ray Diffraction.

Single-crystal X-ray studies were carried out

using a Bruker D8 Venture diffractometer equipped with a Photon III CCD

detector, with graphite-monochromatized Mo

radiation (

=

0.71073 Å)

and with 30-s exposure time per frame; the detector-to-sample distance

was 7 cm.

Data Availability.

All study data are included in the article and/or

SI Appendix

ACKNOWLEDGMENTS.

L.B. is funded by the MIUR-PRIN2017 project

“

TEOREM - deciphering geological processes using Terrestrial and Extrater-

restrial ORE Minerals

”

, prot. 2017AK8C32 (Principal Investigator: L.B.). P.J.S.

was supported in part by the Princeton University Innovation Fund for New

Ideas in the Natural Sciences; and P.D.A. was supported in part by NSF Award

1725349. We thank Walter Steurer, William Steinhardt, and Bill Press for

useful exchanges and Teresa Salvatici for the high-resolution pictures of

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